the major issue with this approach is that we'd have to lock a lot of good threads often, stifling discussion. Deleting allows people to not even feel the temptation to respond to shitposting and trolling, and continue with the thread as if the shitfit that derailed it into shitland didnt happen.
And a ban is only as long as their IP stays the same, which is to say, usually not freaking long. Deleting is our only real tool for effective moderation in most circumstances, deletes are usually coupled with a ban of course. We have, to my knowledge, only used the NUKE EVERYTHING button twice, and both times were because of consistent, willful, and flagrant repeated shitposting, ban evasion, and whatnot, and at that point our only weapon is to take away all the attention they are seeking by eliminating their presence totally. This is a last resort option and as i said, is exceedingly rare and, as far as I know, both times have been by me.
And as i said above, we on staff cannot adress people "feeling" like things are inconsistent, in order to take action if it is needed, i need people to report to the admins via IRC or E-mail specific instances of questionable moderation if and when it occurs. We cannot take action based on feelings, that way leads to madness.
We're aware of the importance of the users trusting the staff, and by and large I feel like we manage to address most concerns quickly and rationally, but realize that as I've said, running an imageboard is an imperfect science, and we have to constantly modify what we are doing to respond to what is going on with the boards.