My first ever bike was a little kid's bike with training wheels. My next bike was a mountain bike. Up until recently I had ridden mountain bikes exclusively. Back where I used to live in Australia I used to live in the country and had easy access to off road trails.
Then when I moved to Thailand I intended to buy a mountain bike. They are after all cheaper. But then I started to think, there are no mountains in Bangkok. At best I would have to load my bike into the car for a few hours of driving to get to anywhere that I could truely use a mountain bike.
So I bought a road bike instead. I have come to realise that a road bike is a far better fit for Bangkok roads.