Because RPG fans make products and give them away for the fun of it, and they're of comparable quality to the products that cost money (in 'game usefulness' if not production values). For example I found this recently. So this hobby is better off than almost any other.
Thats the irony of the other thread...we have more rpgs and rpg stuff--free, in print, out of print, pdf, online/electronic--then ever. And more ways to play them and meet other players.
BFRPG, a full, high-quality "retro-clone" is available for free as a PDF - along with a sizable number of free PDF supplements. In print it costs some money, but even then its author Chris Gonnerman has chosen not to profit from its sale on Lulu but rather lower its price to the lowest possible minimum.
And there is an entire community on the Dragonsfoot forums supporting it and producing a good amount of supplements for it free of charge just for the fun of it.