Obnoxious creatures they are, always trying to take the shine from mosses. Mosses don't need symbiosis because they're perfectly able to survive harsh conditions by themselves. There's been hardly a need to change their perfect designs for millions of years.

Lichens are just the result of symbiotic relationships formed whenever fungi and algae or cyanobacteria feel like doing it. They're a promiscuous lot. Promiscuous scabs on a rock.