Liberals want to regulate everything because they don't trust other people to do the right thing for themselves or for others. Why don't they trust other people? What do they know about human nature that I don't know? Well, they know their own nature, that's for sure. I must conclude, therefore, that liberals want to regulate everything because they don't trust themselves to do the right thing for themselves or for others.
(Of course, there's also noblesse oblige and guilt.)