100% agree with this. I worked from home for myself for about 5 years and decided to go back to work just because of that. Worked for about 6 years and recently went back to doing freelance work again a few months ago and am already looking into getting a job somewhere again, (at least part-time) just for the social aspect of things.
It's bad when you leave the house and think to yourself, I can't remember the last time I left the house. Oh yeah, it was last week when I went to the grocery store! Going out with friends on the weekends is great but it's not the same thing and not something I always want to do every weekend.
I think when I finally become FI I'll probably find someplace to volunteer a couple of days a week.