There are various reasons I like lasers, first of all there is the obvious - the basic sensory input namely vision, what you perceive with your eyes. The colours are nice to see and the seemingly endless beam of light is intriguing, which brings me onto my second point - the psychology of seeing it. Seeing is believing and to see a beam of light come out of the laser and travel to infinity says to our instinctive mind that the beam must be solid. it is quite clearly not however and even if we don't realise it this is a concept our minds find interesting and bizarre. It's the reason why when you turn on any visible beam laser you usually need no words to describe why you like it and brings me to the very subject - how I explain my interest in the lasers.
Outside of science fiction most people have never seen, or are aware of the existence of, visible beam lasers. Usually switching it on is all you need to do to justify the fascination.
As an addendum, anyone who thinks lasers don't have a purpose just has to think of the interest it generates, which is as valid a purpose as any. This is of course aside from all of the "practical" purposes, ie the machines that house many lasers.