It's true that no licence is required to fly a glider, but the consequence of that is that glider pilots are regulated by the clubs from which they fly. In some ways this is more stringent than the regulation imposed on PPLs.
For example:
1. At my club I am not allowed to fly if I am not current. This means (with a Basic Instructor rating) I must have flown within the previous 5 weeks. If not, I must take a flight with an instructor before I am allowed to fly as PIC.
2. If I visit another club with my own aircraft, I will almost never be permitted to fly from that airfield without a flight with an instructor. This (a) informs me about any local issues such as airspace, landmarks, local deals about flying in a MATZ, areas of heavy traffic etc, and (b) enables the club I'm visiting to check out my skills. If they don't like the way I'm flying they won't allow me to launch in my own aircraft, no matter what experience or ratings I have.
I did hear that a Champion of some kind once turned up at an interesting site (v. hilly) with a film crew. He was upset about being required to take a check flight, which indicated that he had no idea how to winch launch and had never flown at a similarly difficult site. So pilot and film crew left hurriedly.