Flags are as valid for curation as votes in that they affect rewards and we don't want them going to junk that gives this platform a bad reputation.
The so-called bid bots may choose to take some responsibility for what they vote on. I saw at least one retracted their vote from this user and I've seen others add bad actors to a blacklist thanks to the efforts of those who look for junk. Do the others care about anything apart from a quick profit?
I only flag what's bad for Steem.
I don't mind the idea of the bidbots, but I do agree it would be nice if they helped clean up after themselves.
In any case, we just have to ensure those who abuse with bots aren't profitable and then they will think twice.