Apple devs as well as application developers— menu bar icons are clearly a neglected corner of the ecosystem in that Apple would prefer that app devs not persist icons in the menu bar at all. But the feature is nonetheless wildly popular as the nearest systray-alike functionality on macOS.
Not really. Even in the case where every single app has a good reason to have a menu bar icon, but you're still left with the fact that macOS doesn't let you manage them.
Or maybe they don't all have a good reason but you don't really have a choice about running them (e.g., on your work computer).
If you are visually impaired, you also likely have greatly reduced space for those icons, especially when undocked. (This issue plagues me personally.) In that case, this is not merely a clutter issue: app icons will simply be truncated from the menu bar, and in some cases that may mean that some functionality is just totally inaccessible to you.