If you, dear xhevahir, wanted to buy a math phd attempt and had the chops, you could self-fund the training, courses, and examinations of a Math PhD, and it'd be up to your own abilities to finish.
But nobody, nowhere, would (should!) stop you because "the jobs" aren't there. You could do it because you can find the money to do it.
Asking universities to set their intake numbers according to the perceived demand 5+ years down the road (let alone the coursework + specialization of those PhDs)? Madness - they'd effectively be planning the whole economy at that point.