Because codes 1 and 2 are fairly well known.
Most people in the know/willing to put in 30 secs on google can figure them out.
And how do you find more members, if the groups are hidden/private? Tbh I've got no issue with the codes, if you prefer it be like reddit where people sell access to content, by all means, but this is basically a socialist commune at this point. I mean look at the past 12 hours? Tons of naked links. People come from reddit to take the links to sell, lol. All people are asking in return is to be a contributing member of the forum, and contributing really isn't limited to buying subscriptions/uploading new scenes.
Being social and not needy/whiny works wonders. Not saying you do it, but a lot of the beggars would fare much better if they just lurked and decided to assimilate into the culture, rather than just posting a pic and asking for a drop. I've not spent a single dollar, but I do share things I know/picked up along the way, like tempmail.org when people needed to find a way to make easy mega accounts when links were getting killed. Reuploading stuff that been posted before helps too. There's a TON of ways you can contribute and eat like an absolute glutton at the same time, without necessarily "buying in"
It's a social forum. Humans are social creatures. Entitlement doesn't look good at all.