Most people who ride fixed will have a hard time separating the fun from the practical. For example I love being able to feel the texture of whatever is under the rear wheel. Is this useful? I guess you could cook up some justification that has to do with traction etc. Does it make cycling more fun? Hell Yes. Something about that level of integration with your environment is pleasing on an intuitive level.

You're looking for someone to explain why riding a bike is rational on a parameter by parameter basis and for most people pleasure is an important parameter. At some really trivial level we do everything we do because it makes us feel good. Why are you so averse to people bringing this up?

**Edited w. qualifier for andre nickatina**