Not disagreeing about the technique, but for the record Geddy didn't start as a single finger player - that's where he's ended up. In reality he uses three distinct finger styles: single finger plucking, two finger playing, and strumming in a flamenco-ish manner.
The single finger playing provides a very different rhythmic feel as compared to two finger playing. The technique serves the material.
Counterintuitively, single finger doesn't slow one down. Its not so rigid that you can't double finger for quick passages and fills. It's an interesting tool to add to the bag.