Comment by mewpmewp2
1 day ago
A lot of the time it's not software developers who define it and it's about the budget. Usually it's the product decision. E.g. an agency who has constant recurring experience with it might indicate that supporting N% browsers costs this much with cost increasing the higher the percentage. E.g. you want to use CSS flex you might get 97% to 99% of all World users, because there's going to be certain percentage for which it won't work. If you claim to support those old browsers you will need to test with them too and be able to easily spin up etc It's not just knowledge of what you can or can't use, it will be extra permutations of testing everything.
In my experience usually it's the software developers trying to push blame onto other people. Sometimes it's a total rewrite or a new product and you actually have to ask how far back to bother supporting (devs are still the ones who ask this). But most times when support is dropped from an existing product it's because a dev brought the question up first.