Peering just means that two AS physically connect to each other directly. Whether this peering is paid or not is independent from the technical implementation.
Just nearly everybody except Telekom is doing this on a liberal and informal not-even-handshake basis. On ISP scale, you either invest in infrastructure, or pay rent for network ports or cross-links, and you generally want your traffic usage to be smooth without spikes, and also go to the destination without going through your expensive ports more than once. So general connectivity is more important than any kind of traffic metering.