I like WesleyDavid's formula for flagging; personally I am far more likely to downvote bad answers (and/or comment as to why they are bad) than to suggest they be completely removed.
I suspect this apparent predilection for flagging comes from a few different (and sometimes overlapping) motivations:
- Flagging sort of passes the problem on to someone else.
- Downvotes cost rep, and some people are far too focused on rep gain.
- IMHO, far too many sysadmins have this visceral hate for anything they consider to be "stupidity". I suspect this is often coupled with some amount of feeling that "I am certain the given answer is stupid/wrong, but conversely I am not certain of the canonical right answer."
Personally I've been a bit dismayed by the abrupt and binary responses to some bad answers/questions I've seen around here. To me it seems that there is often a voiced impulse to blast things into oblivion rather than expend the time and consideration necessary to improve them.