Anecdote here. I feel the same: when I had a job that was 30% coding, I did personal coding on the side. Now that I have a job that is 90% coding, I don't. I only have so much energy for coding, and by the time I get home, although I still have fun ideas that I'd like to do, I just don't have the energy to start writing anymore code. If I forced myself to code continuously, the overall quality of all my code would drop a lot. It's fun, yes, but it's also just too mentally taxing.

I recognize if I was planning to go on the market, though, I'd need to force myself to write some "on the side" code so I'd have a recent portfolio to show. I think it's just part of the expectation, the same way I would have to take time to write cover letters, etc.

Burnout is not exclusive to software developers. Any human needs to de-stress - this is well known and documented by the medical professionals.