I disagree.
There are times when I purposefully do not upgrade it. Generally when behind and being in range for the effect to work could be dangerous. The basic sweeper can be cast at a range, and will work at that location for its duration. This means I can throw it on the dragon pit and leave vs having to stay in range till the wards are cleared and to maintain the reveal effects.
Usually a few levels later, or another item later I will feel safer upgrading the sweeper to teir 2 when staying in range to block vision, disable traps, and clear wards is safer.
Automatically upgrading it would take that away from me.