Because it would result in 5% of the hourly wages paid working force would see their wages increase, which would directly hurt those businesses who hire people that make minimum wage.
Restaurants, Best Buy, Walmart, Target, basically any place someone 25 an under works would see a $2/hr increase in wages.

have 50 employees? $2/hr for 40 hour a week employees=$ $16000 a month increase (CHECK MY MATH BLANK)

Its not just about the $9/hr employees, its about everyone above them as well. What happens to the guy making $10/hr when the 16 year old kid starts making $9 instead of $7.50? Well he has to get a raise too right? I mean if we are just arbitrarily handing out raises to make people "survive" why not do it for everyone?

As those lower end wages raise, laws of economics dictate that the curve will shift upward. Prices will rise because you jut added a $16k/month expense to the business at minimum. Thats if you keep everyone else salary the same. Minimum wage is there to protect people from child labor laws, and establish a minimum standard of living for a short period of time. It was NEVER meant to be a CAREER wage.

$1200/month is enough to live on in most areas when you are 16-25.