My husband and I were like this for a bit when our kids were tiny for several reasons.
The biggest reason was I was assaulted & raped, left as a bloody mess, and it took me ages to regain my confidence, even longer to feel comfortable with others without essentially having him as back-up.
Strangers treated me better when he was around than when I was on my own, and we found the same was reversed too when our kids were involved. This may have improved, but some people were downright vile to him being a man with tiny kids without a woman involved.
We married as teens, had kids young, don't live near either of our families, and for a few years didn't really have anyone else in our daily lives we could rely on. I kept trying and would get knocked back to the point I'd go through periods of depression and not trying. I didn't have people to go to coffee mornings or lunches with for several years, not because I went out with my husband, but because when I went out alone to the toddler groups or even to the bloody shops, I'd get mocked for my age, or my accent and dialect, or my mobility devices, or that I wore a headcovering. I've been followed around shops having people shout shite at me. I ended up moving areas, but that's just having to start over again.
We also both have disabilities, some of which were new then that we were still working out. What was easy for other people wasn't so easy.
There is a lot out there on how a significant part of the population is isolated. Mine wore me down to the bone and yeah, I'd get to points where I'd give up trying to be more social when trying was hurting too much. That habit can get ingrained, many areas have few spaces for people to try again socially for adults, and people get stuck.