How did you come to this conclusion? I can can goto Starbucks, restaurants, supermarkets, and youth sporting events and very commonly see a tablet somewhere. Generally it is the iPad rarely it is something else, if you want you could say tablets aren't useful, just iPads but that isn't true. You have your head in the sand, tablets are here until somebody thinks of something's better and it isn't a laptop.
Here is a prediction by summer of 2012 if iPad 3 is out the total of all iPads plus kindle Fire will surpass 100 million units sold. Just because , HP, and HTC have been failing to sell tablets does not mean that tablets are failing. There are plenty of computers that failed when they first started moving away from Mainframes as the only computing model. Comodore had several failed models, the Tandy was only mildly successful, Atari made a computer that failed, and other companies at the time made plenty of failure as well. I was only a kid at the time so I can't remember them all and I'm too lazy to research it.