If it was easier to do the work yourself I think more would out of privacy, price, and longevity concerns.

Separate modem and router. Using my own modem kicks out my ISP from individual MAC so they can’t see as much device level info. Plus they wouldn’t let me setup a guest network. And now I can monitor the devices myself which is mostly for fun. I run a device VPN when I don’t want them to see traffic but I’ll likely set it up network wide when I have time, which I couldn’t do on their system.