In the US the bicycle is considered a toy, a recreational device or as exercise equipment. That's why bike shops are filled with mountain bikes. Travel they leave to other vehicle retailers, i.e. auto dealerships. This is a big mistake. Don't buy a mountain bike just because the sales person has lots of them to sell.
Mountain bikes are fine for many things, even commuting.
However, most people never get near a trail with their mountain bike. Those fat knobby tires may really dig into the dirt on a stretch of fire road. But they add lots of rolling resistance on pavement. Don't believe it. I can tell you from experience that large glass fragments, nails and pushpins can puncture mountain bike tires too.