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.