I think it's all very personal. We are FI but not RE, and that decision was based on the following:
1. Staying married. DH is a natural spendypants and wants a much higher level of luxury in retirement than our current investments would support, and has no desire to quit yet.
2. Access to high-level, intellectually stimulating work in the area I've trained for. I have a very low boredom threshold, and while I could volunteer or set up my own shop, I would not have access to the same brain-twister work I enjoy. (This is also the big driver for DH: he is doing very advanced tech work that requires investments that start with a "B," so once he quits, that's all gone) I also really, really like the people I work with -- and I'm an introvert, so that doesn't come easily. And the work I do matters to them, too -- not just financially, but I have a big responsibility within the firm, and people appreciate my doing it. Plus they think I'm wicked smart, which is good for my ego.
3. Freedom to do whatever I want regardless of the cost -- to treat other people, or myself, to things that I literally never even thought were possible. This one is hard for me to wrap my head around, because I grew up not just poor but frugal-poor, where saving was the priority, and never spent anything on anything more than you absolutely had to was a moral issue. The big leap for me was when I bought my StupidCar. That was the first truly frivolous big thing that I bought for no other reason than I really, really, really wanted one. And OMG, I *love* it. Every single day.
But I enjoy even more being able to do frivolous stuff for my family, without all the angst and drama that went into persuading myself that it was ok to get that car. So, for ex, we were going to NYC for DD's HS graduation, she is a huge theater nerd, so I went on stubhub and bought tix to a sold-out show as a graduation present and didn't even have to worry about whether/how that (objectively ridiculous) cost might affect my future. After growing up with that kind of freedom so far out of the realm of possibility that it was inconceivable, I really appreciate being able to do something like that once in a while.
(of course, that monetary freedom is offset by much less time freedom, but see point 4).
4. I am externally motivated. Without some deadline, I would happily sit on the couch and run the clicker. It's not a problem when DH and I are off together, because he has things he wants to get done, and I enjoy finding stuff to do with him. But he's working for another @5+ years. I also know that sitting and doing nothing is very bad for my depression. So I'm going to need something to do that uses my brain and makes me feel useful. Which means that until DH retires and we come up with a better plan to spend our days, I need either a job or a volunteer gig. Which brings me back to #1. And really, if I'm going to be going somewhere on a schedule to do something productive every day, I might as well be getting paid a metric shit-ton of money for it.
tl;dr: I'm really fucking lazy, but being lazy bores the shit out of me and triggers bad depressive spirals. So given that I'm going to need to be busy anyway, I enjoy staying busy at something that I find interesting and challenging, and it turns out I really like getting paid for it.