My current employer technically forbids me from showing photographs of my dog to my mom. Naturally, no one would ever care if I did, but my contract explicitly considers any distribution of anything I produce that can be copyrighted (at work or not) an act corporate espionage.
https://www.exratione.com/2011/11/the-miserable-state-of-int...
In large corporations, an exception to a blanket IP contract would require approval by fairly high ranking people in both HR and Legal. When you have >10,000 employees, individual exceptions simply don't happen for anyone under any circumstances.
My experience is only reflective of very large companies. I doubt it's representative of smaller employers.
My last employer was a startup and I had this stricken... as well had privisions in place so I could do outside consulting as long as it wasn't in a competitive industry (this they may have given me as I came to them initially doing part-time consulting).
The place I worked at before, a 15k person corp, is a place I wouldn't have even thought of asking for things like that. It would have a couple weeks just to have gotten a turnaround through HR and legal.