I have 2 guesses as to why.
- To prevent spam. This would make it hard for spammers to just name their topics
Go to <Some scam website> for 5 bitcoin. They would need to at least add an extra character. - To make people be more creative and help with the search. So instead of
I am having trouble with x topic5 times you would need to explain in more detail what your problem is in the title.