Well, depends on what you do. Sure, it can be nice to be offline for some coding, but most work these days, even predominantly coding work, is a team affair and requires communication to work well. Further, being able to get quick access to docs, tickets, etc. is quite useful.

But also, if one is responsible for the functioning of significant amounts of infrastructure, then it's not so great to have to worry about internet flaking out in the middle of working through production issues.

But yeah if you were working on something solo, then bad internet wouldn't matter as much.

People do different work and different things. Some people probably also get reinvogorated after watching HD video streams as a break.

Personally, I prefer fast internet and blocking sites via hosts file, extension, or an app. But I lack a certain amount of self discipline. I doubt being without fast internet for long periods of times and not wasting because of that outweighs having slow internet after the initial change of pace.