They're not intended for all 'professional' users either. Not all 'professional' software uses multiple cores effectively, at least not beyond 4 (which has been mainstream for a long time now).
For example, Photoshop actually doesn't benefit from more than 4 cores. A quad i5 is fine for Photoshop, a quad i7 will squeeze a tiny bit more performance out thanks to the extra threads, but anything above that it's wasted on Photoshop. Reference.
I don't believe that's true for Photoshop... not entirely anyway, as I have read certain filters will use more and there are instances where more than 4 WILL be utilised. But the casual user will of course be extremely unlikely to encounter this... but I'm not talking about casual users.
Of course not ALL professional users will need these CPU's. I didn't say that lol, but these are the types of people who WILL use them. Gamers certainly won't. But of course, as Jigger suggests, the uneducated are probably the ones buying them in droves lol!
Doesn't mean you can't buy the new shiny if you want it... why not, go nuts! That's not the point though.