There's been 100 million iPad's alone sold since they came on the market, they are absolutely everywhere, lol. That's not even counting the other makes and models, Android, Windows tablets, hell - even touchpads and playbooks, not to mention low cost ones like the Kindle Fire.
Most people realize they are consumption devices and not laptop replacements, and for that they do just fine. Tacking on a keyboard and mouse to a tablet like an iPad is inelegant at best as the thing still is an "app machine" solely and not a real computer, so for the extra $200 a Mac Air is a better choice.
Not to say you CAN'T create content or do more productive things on a tablet.
GarageBand for iOS is great, but overall the iPad and similar things are not really comparable to a "real" pc, IMO.