A few things.
First: As Dice4Hire said, the majority of Magic Item Daily Powers honestly aren't that great. You should be looking for properties, with powers being a (situational) bonus.
Second: TarionzCousin- that would be a terribly unbalanced item as-written, not only because it would grant Action Points, but also because there's no reason to buy a higher-level version than a lower-level version. I'm sure a level 30 character would love to buy a hundred level 5 versions.
Third: The reason Magic Item Dailies are limited are, as AbdulAlhazred said, for balance reasons. Many magic items' dailies do not scale with level (and don't need to), meaning that a lower-level version is just as potent as a higher-level version. There would be nothing stopping a high-level character from buying a dozen lower-level items and using those abilities over and over.
Limiting Magic Item Dailies only feels like a restriction if you are under the assumption that they should act like class dailies. This is a fallacy; if Magic Item Daily powers were called something else, like "Magic Item Specials" instead of "Daily Powers", less people would associate the two. Magic Item Dailies are NOT the same as class daily powers- they are less powerful, much more situational, but are not permanent, as a player's daily power. A class daily can't be switched out on a whim (barring certain cases)- whereas you can pick up one magic item one day, and pick up a different one the next day, if the situation warrants it. Overall, magic item dailies follow completely different rules from class dailies. Once you understand that, it feels like less of a restriction.