Simple example, I sold my car to Carvana the other day and just baaaarely pulled it off using Chrome and Firefox. In Chrome the upload image wizard would get a JS exception. That part of the app miraculously worked in FF, but virtually the entire rest of the site was mired in issues as it's obvious Carvana devs don't test in FF. I pulled off the transaction by bouncing between the two.
Even worse, most non-technical people think they did something wrong when they encounter a bug.
Software that is bloated and slow but stable and rock solid? I'd gladly take it at this point.