I don't, 99.9% of the time.

But when your browser has a 2% market share worldwide, some developers won't bother to test on it. And if your setup is even more obscure (I use Firefox on Linux with an adblocker and third-party cookies blocked and DRM disabled and autoplaying video disabled and so on) making you rare even among that 2%, sometimes sites won't have tested with your specific configuration.

It's useful to have a second browser around, as a fallback when a site is broken. Uploading images when creating a listing on ebay is broken, but I don't have to figure out which element of my setup is breaking it, I can just switch to the other browser.