It's not that they want to make more money...it's for liability reasons. If a car comes into Sam's Club for tires (where I work) we have to put the same speed rating on or higher. If we were to put a lower speed rating on and they were to have problems and get in an accident we would be liable. Most reputable tire shops follow the same rules. It really sucks for Toyota Camry owners. Toyota decided to put V rated tires on them, so we can only install V or higher. Now yes, I know your Toyota Camry won't go over 110mph, but that's besides the point. It will majorly change handling characteristics going to a T rated tire.
Now if you brought your 2007 G6 into my shop, I would interchange with T rated if you want because I know hat G6 came with both. Just as much if you brought in your car with 225/50/17 I wouldn't blink an eye at installing 215/55/17 because I know It was also a size used interchangeably with no rhyme or reason.
2009 Performance Red Metallic Base Sedan 2.4L
Ebony Leather, Sunroof, and 6-Disk
17" Konig Zero-In Wheels / Michelins