It would be easy to blame the customers. But let's look in the mirror -- how do I make purchase decisions as a customer?
Actually, not a good example, because I usually don't buy software. OK, I buy Windows, but... I don't feel like I have a choice between more polished and less polished versions of Windows. Other than that, I use free software. When I use software at work, someone else made the decision and I had zero input. And that kind of software usually sucks (now I am thinking of Confluence, Jira, and other user-hostile monstrosities).
So I guess a part of the answer is that if you sell software to business, there is no need to make it nice, because the people who decide whether the company buys it are not the ones who will be stuck with using it.