[Shirik]

Instead of asking why not upload to multiple sites, why don't you ask "why don't I check all sites?"

Truth be told, it is much easier to check multiple sites for an addon than it is to upload to all of them. That is the complaint of many addon authors. Several I know argue that they don't upload to multiple sites simply because they do not want to deal with users that are so lazy that they cannot check them.

WoWI, Curse, and Incgamers all have features to automatically notify you when updates are available, and all have automatic updater clients that can satisfy that need. If you feel it's too complex to have multiple clients installed, then ask them to write a module for Minion.