I've always been doing this since 1E AD&D.
There appears to be an implicit assumption of the players having magic weapons of an appropriate level. I don't know if 4E was originally design this way, but in practice this assumption makes the combat encounters less "grinding". But on the other hand, this assumption does make the combat encounters somewhat "cookie cutter" regardless of level. In a previous recent thread,
http://www.enworld.org/forum/d-d-4th-edition-rules/270715-1-level-instead-level.html
it was shown that the to-hit roll scales approximately as:
~ d20 + level
for an attack using a player's primary stat along with the assumptions of magic weapon enhancement and regular player ability stat increases.
Yes the system is designed assuming that over the course of their adventures characters will increase their weapon, armour and neck items.
This is built into the system.
I've read that whole thread and I can't work out at all why all the proposed changes are a) needed and b) any better.