Because:
- If you install any new software that needs updating, you don't need to update your alias.
- If any software makes changes that break your alias, (theoretically) the bit of software should be able to fix it quickly, without you needing to pay any attention to it.
- The bit of software can more easily do advanced things than the simple alias. For example, I added functionality to update JetBrains Toolbox and IDE's installed with it. A simple alias could not do this, because Toolbox does not have a simple update command, however I made it work by enabling automatic updates temporarily, and then inspecting the log for updates. Now the end-user doesn't have to think about this at all. Other things that could be done but are not implemented yet include parallelization, and listing updated components in a neat summary (PR linked).
Of course if you're a minimalist, then you probably don't have that much stuff that needs upgrading in the first place. For me personally I have deb-get, uv, cargo, and flatpak, to name a few; the alias was getting longer and longer until I was able to remove it completely by switching to Topgrade.