Years ago I read they have a policy of pressuring studios to provide censored versions of movies specifically for Blockbuster. In many markets Blockbuster was the only video store. They had the leverage, so studios bent to their will and did the censoring. Sometimes the censored version was the only version, if the studio did not put more money into separate uncensored copies.

I was in a Blockbuster once. No porn there, much higher prices, never went back.