It's not about "control" and "spying". The fact is it is policing that has been made extremely hard due to technology.
silk road was only busted because the guy had his http proxy responding on the VPS's IP and not just the tor eth. Silly mistake and unfathomably good luck that someone in the investigating team was just googling around.
The politicians are lay people, and only have one tool in their toolbox: laws. So every solution is a legal one.
"Sorry we can't catch the people sexually abusing one million children every year because they use a VPN." Solution? Create a law requiring VPNs to be registered to a user with their address. There's no conspiracy here - it's simple cause and effect. This is a contrived worst case example because this level of accountability? is not currently proposed.
I would prefer other solutions, but these solutions are firstly much easier for the politicians to understand and also much cheaper to implement and see results.