Lots have been said, but I am going to say what I will.
I check drums first for two reasons:
1. They take the most time. As said before, 8-12 mics. (This doesn't mean they are most important)
2. I start with drums on my console. Ch 1-8. I then check 9 (bass) 10(guitar) and so on... If I can, I like to move from channels 1-Whatever in order. Drums are even my first two sub groups. That doesn't mean I consider them most important.
This means vocals last. Hell, I don't usually check vocals (aside from line check) until they play a song in sound check. Why? Because most vocalists don't actually SING until they are with music. I put my mix together here.
I would like to add that whomever was complaining about checking drums first, the drums are one instrument. If I hear 12 different mics then I know I am in the presence of a bad engineer. If I hear a mix centered around drums it could be a talented engineer, just a bit misguided in the art mix.