What do you really need? I still meet people all the time who adore their netbooks (though many did also ditch them as soon as they actually had to use them – I’m seeing that with some tablets, not so often with iPads).
Besides, why do you assume that those people are buying their second iPad? Maybe they are buying an iPad for their kids? Maybe those who didn’t want to get one because of price are now buying one?
I really don’t get that tablets are supposedly not useful. I love my tablet. I use it all the time to read, surf, browse and write e-mails. It does nearly all the things I used to love doing on my PC so much better. It’s just all-around awesome in every respect, worth every single cent. Simply perfect. There has been no other computer I ever owned I liked as much as my tablet. I would not be surprised if quite a few other people also feel that way, maybe to a lesser degree.