I'm not going to speak for the owner but I can say from personal experience it's not so easy to just set up a pay system like that, where you take money you need a customer service department to deal with refunds, non-working accounts, figure out a policy for people buying an account and then making their password public so anyone can log into it and lurk ad-free, you have to figure out how the ban policy works with paid users, you have to write a terms of service, have bookkeeping in place for tax purposes to report the income...
Maybe today there are automated services that handle it all for you, but there's a reason you tend to only see Gold services offered by sites run by large businesses (ESPN, Wall Street Journal, etc). The moment you start charging people everything gets more complicated.