Truly enforcing this kind of ban would require a level of control over the internet much greater than China's. They actually do ban VPN use, yet plenty of Chinese people still use them, and not due to lack of trying on the part of the enforcers. You can basically never plug all the holes without essentially shutting off the whole internet.

China spends roughly $6.6B censoring their internet every year [1]. Much of that probably goes to "guiding" public opinion as opposed to simply removing undesirable content, but factoring in purchasing power parity of labor and parts, let's assume the US would spend roughly the same amount just to enforce a VPN ban mostly effectively. That doesn't sound like a position that will win elections.

[1]: https://jamestown.org/buying-silence-the-price-of-internet-c...

China knows about all VPNs, but doesn't ban them outside of political turmoil. When people start protesting, then they cut off all VPNs. They just don't do it during "peace time" because they don't want VPN users to find out which kinda of VPNs they can't block. They also apply different rules to foreigners and locals, because they want to give a better impression of their country.

They don't need perfect enforcement, or even good enforcement. The purpose is to make VPN use criminal. Then you have a large group of people getting away with criminal activity which you can go after on an individual case-by-case basis, depending on your level of compliance or troublemaking in other areas.

China doesn’t actually want to ban VPNs. They want a list of all possible dissidents so they can actively monitor them. “Banning” VPNs just lets them narrow down the list of people who might engage in wrong think.