Because SMN is a SUPPORT JOB. Again, I'll list the things that make not curing inexcusable.

A. SMN has a huge MP pool. The largest MP pool in the game.
B. When using an avatar under favor, especially Diabolos, MP is not an issue. I get something like 5 refresh per tic with my gear under Diabolos favor, so it is VERY hard for me to run out of MP.
C. When using avatar's favor, the point is to NOT attack. If you attack, the favor buff resets.
D. More often than not, the WHMs are focused on keeping the tanks and DD alive. BLM are the secondary goal.
E. BLM have to constantly keep their enmity in check. If they don't, it's next to impossible to pull hate off of them in an emergency. Curing adds hate.

If you are in a party with BLM in an event, and you are being expected to give them refresh, not curing them is inexcusable and a sign of a bad SMN.

And in regards to auto attack, I said that my avatar shouldn't be attacking slept mobs unless I tell it to. That's a very simple AI fix.