There is no punishment on bumping old threads as long as the thread is important, because we are encouraging the use of search function of the forum to be able to access some threads you might have in mind to create something similar, so that we can have limited number of similar threads; if the thread is found, the next thing is to read the thread and maybe comment under in case you are not satisfied or if you have question to ask about the discussion or you have your idea you wants to share your thoughts about the subject of discussion. It is better to reply on the existing topic of discussion than to create new thread according to this discussion.
Because of spam, the bump score applied in some boards.
Bumping changes on some boards. In those boards, bumping a thread can not be abused.
In addition, forum has rule against necro pumps that are annoying and not allowed.
The strong guideline is 1 bump per 24 hours per thread. Additionally, bumps should not be annoying, which needs to be determined subjectively. If a user bumps 10 threads every day, that's annoying. If a user bumps 3 threads at the same time for some good reason, then this may not be annoying.
Reason is simple, people don't want to read what they see, and with such lazy people, they surely don't spend time for searching anything. With them, if you bump a helpful thread, they don't read it too. It's similarly to how they ignored pinned threads and did not read such helpful threads.