Three browsers open is not a requirement for the vast majority of folks.
Every developer who makes frontend things for the web should have a minimum of three browsers (Chrome, Firefox, Safari, but maybe others as well) open any time they're testing or debugging their code. That's quite a lot of developers.
Nah, most of us go browser by browser I think. I think I've been going with two browsers open at most the last 5 years, and at my current employer I'm so reliant on browserstack that I don't even have anything other than chrome running.
Every developer who makes frontend things for the web should have a minimum of three browsers (Chrome, Firefox, Safari, but maybe others as well) open any time they're testing or debugging their code. That's quite a lot of developers.