I use multiple browsers because not everyone writes code that works across all browsers. I own several screwdrivers for the same reason: not everyone makes screws with the same kind of head on them.
This Mastodon instance is for people interested in technology. Discussions aren't limited to technology, because tech folks shouldn't be limited to technology either!
also, not all browsers implement standards the same way (or at all in some cases). so it's not just website builders but browser builders as well.