There are two different types of cheater. There's the one who is always going to be on the lookout for someone to shag, but there is also the one, who would define themselves as fundamentally loyal, good people, but who put themselves in positions where an affair 'just happens'.
For the second type of cheater, it happens because they have not observed appropriate boundaries with people outside their relationship.
I don't understand why any wife (or husband) would happily sit back while their spouse deliberately puts themselves in a social situation that creates intimacy with someone other than themselves. That means cosy evening dinners, while the spouse is at home with the kids.
My dh goes to work so he can earn money to support our family life. When he is not at work, I expect him to get home and actually partake in that family life. He is not at work to make friends and socialise. If there is time and money for cosy dinners, I expect him to be having them with me.
Call me old fashioned but I think the OP's dh is taking the piss. It may well be innocent, but it is definitely inappropriate.
I am also cynical, but plenty of people hide in plain sight - they think you won't possibly suspect them because they've been so up front!