Not to mention any government system will be both more expensive and less effective than just solving the problem yourself. It takes all one ONE afternoon to look up how to do some network level blocking for pornography, there are entire guides, resources, open source softwares and step by step plans you can find and download to make it exceedingly hard for anyone on a network you control to get any sort of porn.
If the argument is people won't bother, won't try, or are too stupid for it, I'm not buying it. Parenthood is an obligation, not a option, and I've seen retards who don't know the first thing about the internet set up entire IPTV DVR setups to steal every streaming service they can find, and do so over a weekend.
And the cold truth is that if you are such a shitheel parent that you'll let them live off in the goon cave for 14 hours a day, banning porn isn't going to fix or save that kid. Stop trying to shift responsibility for families onto government, it never goes well.