Armored car. No, really!

[gmflex]

Why aren't more cars fitted with these as standard? What are the drawback of these?

Cost 
I recently replaced all 4 tires on my 2009 vetted
And the cost was over $2,100.00
 
Damn goodyear is making a killing on this F1 tires 

[BayGBM]

Why aren't more cars fitted with these as standard? What are the drawback of these?

Are you serious?  $$$

Some cars now do come with runflats as standard, but it is a) much more expensive than a regular tire.  They fold the price into the cost of the car so you don't notice, but it is much more expensive.  b) the ride is not as comfortable as a traditional tire in my opinion.  My neighbor here has an BMW M5 and it has runflats.  It is an impressive vehicle to be sure, but it is not the same as the alternative.