There's certainly some truth to that - in an ideal world, those rules would not exist. But here's the problem: good and bad posts are often a matter of opinion. Some people simply don't understand what constitutes either. So in 99.9% of cases, very short posts have very little or nothing to contribute, so they, as a whole, need to be avoided. In terms of bumping, there is rarely anything that requires a new post and can't be added to the previous one. If you're referring to reviving threads, then I believe that is up to the moderator's discretion, but in most cases, either the thread or the offending post is no longer at all relevant.
Here's the thing: rules are always going to inconvenience someone with good intentions and where it might not be necessary, but these rules are required to stop the people who will take advantage of any freedom.