PHPBB is constantly full of security holes and on the sites I've used it on in the past, we were hacked repeatedly. Also, neither invision nor phpbb have importers for the the old version of UBB that we were using. Dropping some cash in order to save years worth of history is worth it. It was never an issue of cost -it's an issue of TIME. We can do all these features in a way that won't be annoying on the various boards, but it takes experienced programmers time to implement them. I picked vb because it had the importer and it actually ran decently fast. If you look at PHPBB and invision board, it literally takes DOZENS of sql queries to generate a single page. It's insane, and on a popular board, it will bring the server to its knees.
This is another one of those issues for non-logged in users. I don't login every time I visit the forums, and I shouldn't HAVE TO unless I'm going to post. So unless we get an option to turn signatures OFF BY DEFAULT and force the people who like them to manually turn them on, this isn't a viable option. Massassi didn't get where it is today by ignoring the folks who don't feel like signing up for an account or logging in.
BTW: I did this only after a discussion on the admin forum - someone said that turning off vbcode would allow urls still, but obviously that isn't the case.
Because it often takes less effort to disable an option than spend hours every day moderating something. And don't suggest "hire more admins" because it's hard enough to manage the number we have already.