Believe it or not, some people prefer not to live in a world of filth. It's the same reason why there are laws against other vices. Gambling, drugs, alcohol...
It's not about stopping things 100%. It's a deterrent and a completely non-controversial thing.
You can circumvent the system and watch filth in your own house. No one is kicking down doors to prevent you from running one out. But the people of their own state voted to deter the free flow of pornography as a standard. Porn hub pulled out of the state. The deterrent worked.
