If I may… They do. The devs definitely pay attention and put work into them. Believe me that if they didn’t, using Discourse would be a way less pleasurable experience.
The thing is that there’s so many details to pay attention to that they realistically can’t put resources into all of them – even after years.
pr-welcome tags are sometimes used to encourage users to contribute, as Discourse is open source, but some welcomed features need to be thought thoroughly design-wise, and then having an external developer sending a PR is not always the best solution.