There can be quite a number of distro-specific quirks to bear in mind if you're targeting more than one, enough so that as a downstream product vendor it's nice

There can be quite a number of distro-specific quirks to bear in mind if you're targeting more than one, enough so that as a downstream product vendor it's nice to only have one or two ideally slowly-moving targets (say, RHEL and Ubuntu LTS) to test on/document/support instead of dozens. In turn it's also nice as an end-user to have a platform with long periods of stability/support so you're not having to rebuild/retune your systems' foundational bits every year. (I have no particular dog in this fight. I mostly left the RedHat ecosystem behind a long time ago, but I understand it's still a big deal for a lot of vendors and clients. From an individual dev/user perspective, I agree that more or less as long as whatever is a posix-y environment, I can figure it out and get my work done, whether it's solaris or slackware or whatever haha.)