The admin of this forum has already done so many ways to prevent overpopulation. One of those is when creating an account the is already a proxy ban wherein you will need to pay for it. Another one is the merit system it give people a hard time to rank up so more likely they will become lazy.
Why we need to control the people from entering into bitcointalk?
It was meant for all the people who wanted to know about bitcoin and other cryptos so admin don't want to restrict the new users.The IP ban is the reduce the alt account creation and the merit system is to restrict the signature spammers who don't know anything about cryptos just filling their weekly quota of posts to getting paid.