Inflating labor pricing with no corresponding increase in productivity will lower the business profits, increase pricing and result in fewer job openings.

If 15hr is good, then 30hr must be great, so just pay all your minimum wage guys 30hr instead. If it works then everyone will hire more and you'll be rich!

Not to mention you'll have to pay the guys who you are already paying more than minimum wage even more since now even the cheap labor makes 15/hr.

No one wants to make the minimum, it's an incentive to do a better job and work your way up the ladder.