First, for full disclosure I am a "Wood Guy" I love wood so this post is written with that bias - just sayin.
Why would anyone use Laminate Flooring on their stairs? Notice the word "flooring" it is manufactured for the floor not the stairs. Flooring companies decided they could make money by offering to put on the stairs as well to match the existing floor. To the homeowner it seems to be a reasonable idea, how would they know the difference. Is it cheaper? Maybe - but over time it does not stand up. If a step is damaged it is very difficult to repair. And trust me; there will be damage at some point. Below are a few pictures showing some of the reasons why I personally do not like the look. You can see each joint and piece of flooring.
In order to use flooring you have to add a solid piece of wood called a "bull nose" to the front of each step. Stepping on that portion over time will make it loose. You can easily see the bull nose piece in the pictures.
Solid Wood treads and risers look beautiful and will stand up to the test of time and all the wear and tear. If something drasitic happens to one of the treads, i.e. drop a piano or so something heavy you can take that tread out and replace it. Solid wood is the way to go.