Not necessarily but I assume some are deceiving their wives in some way. Long story coming up, apologies...
When I was younger I was friends with a man I used to go to school with (so had known him a long time). It was well known in our circle that he and his ex DP were separated. The story he told was that they had casually been together and she said she couldn't have children so they did not use protection and she got pregnant. They werent together and he wasnt sure if she had lied to him. However she had no family in this country so he supported her and saw a lot of his son. Just friendship with his ex DP though. Some of his friends met her briefly in passing to say hello to but she never socialized with us or came to birthdays/weddings/events (as they weren't together). He used to live with his dad but had recently moved in with her, as a favour to her, as she had been struggling with the rent. She had begun working nights and he worked days, so it made sense to be in the same house for childcare and shared bills etc. But they had separate bedrooms and were not "together". I had been in his house and he did have his own room and they appeared to live very separate lives. Things progressed between us and he expressed an interest in a relationship with me but said he didn't want to tell his ex DP just yet as she would threaten to move home (a different UK country, 9 hours drive away) and only see his DC in the summer holidays. This did raise the red flag but I had mutual friends with her. So I asked them the score and they confirmed they definitely weren't together and hadn't even lived together until recently when she began working nights, so he moved in to help her. They confirmed that she regularly said she wanted to take the DC back "home" as she was homesick and missed her family. All sounded right with his story.
Began a relationship with him. Met his friends and extended family and even went to his cousins wedding with him. Nobody mentioned the ex DP and all were lovely. I knew some of them (to say hello to) from our days of being friends. He spent nights away from home at the drop of a hat, held my hand in public, introduced me to people as his girlfriend and picked the phone up whenever I rang. Steady stream of texts (when he wasnt in work). Near the end of our relationship we went on a few day trips with his DC. It was going really well. I even saw him Christmas night. Once his DC was in bed he came to mine.
She found out about us. Within a week they (him included) had packed up their belongings and moved away. Exactly as he predicted. He rang me once they moved and said he was trying to change her mind and he couldnt lose his DC etc. I backed off as I felt he should be with his DC and felt sorry for him. She forced him to delete all his social media.
However it turns out it was all a load of lies. His DP rang me and he later admitted it all. They planned for her to get pregnant as they were very much in love. She was only 19 and far away from home so had nobody. Once she was pregnant he told her he couldn't move in with her as he had to care for his cancer diagnosed dad and she accepted it. His mum had died years before and he had no siblings. He told her most of his money would be going on his dads care and bills so he wouldn't be able to give her money. He couldn't support 2 households. He also told her he earned around 10k less than he actually did. So he convinced her to apply for single parent benefits. Obviously they should tell people they weren't together (in case it gets looked into). He then began dating other people behind her back. He would visit her and his DC every day after work for dinner and then go back to his dads as he couldnt leave his dad overnight. He told his entire family and friends they weren't together and he was helping her and his DC. She agreed with the story so nobody reported her. During this time he was going to the pub regularly and seeing friends (I was part of this group). Burning through any money he had. Meals out, nights out, lads holidays etc. Entire time secretly sleeping with her and her thinking they were a family and he was supporting his dad because he was a lovely guy.
Few years later his dad died. He had nowhere to go as his dads house was sold (he didnt get much as his dad had debts). He loved the single life by then though. So he told her he wasnt sure what he wanted to do as he was depressed and caring for his dad had destroyed his mental health. He didnt want to lose his family but he just didnt know what to do. So he moved in with her, but in his own room. He just needed time. He proposed to her. But they didnt tell anyone, as he wanted to do it "big" once he felt better. He didn't want questions about it from his extended family so she shouldn't tell people they were "back" together. I am unsure if she was still claiming single parent benefits but I know all their finances were separate at this point and they 50/50'd all bills and claimed to be housemates. She could now get a job. The best paid job in her skill set was night work. So she took it. This meant he was free to do whatever he wanted while she worked. She would get home at 7am and take the DC to school and then sleep for the day before picking him up at 3.30pm and doing his dinner. She would put them to bed and then head out to her night job. So all he had to do was not leave the house while DC was asleep in bed. He also had friends (and girlfriends) over in the evenings to watch movies and have games nights etc.
I often wonder whether it was all pre-planned or just "fell" into place. After they moved they were married within 6 months and have since had another DC. They now live 5 minutes away from her parents. None of his friends here have heard from him but I hear occasional news when one of our friends bumps into his Aunties/family. They all just think he "got back together" with her. I guarantee he will return one day with a tale of how abused he was and how he had to do it to see his DC. This happened over 10 years ago and I do wait for karma to catch him, but it hasn't. I often wonder what his life's like now and if hes happy. Also is his wife happy and has she forgiven him.