That's the problem, just be deleted. Why should not punished them ?
I think Mods are too soft on spammers, especially compared to number of spam bots that go around. I've reported many bump bots that just got a post deleted instead of a ban. Not only does that not matter to them, it's not even a punishment as the bump has had it's effect already.
It's probably not about being soft but rather having the time, energy and resources. There's only a few staff members that can ban people for a start and it's incredibly time-consuming to do so not to mention never-ending, and that's why things need to change with the culture here. Also, those specific reports you're talking about may have been handled by someone who doesn't have the ability to ban them, but it's also something staff shouldn't have to be doing and is just seen as a waste of time by most of us at this point without changing the culture of paid bumping which is at least being addressed now with this thread.