Why no deals for long time customers?

Yeah, I just got off the phone with TMO.  Been a customer for years.  They had a BOGO on IPhone 8s, only applying to people who aren't TMO customers.  I thanked the rep for reminding me that its time to change carriers.  Even if other companies only offer a 2 year intro price, it's better than what I am paying now and a few of them have drastically better coverage.  My loyalty as a long time TMO customer only goes as far as they are willing to treat their existing customers the same as new customers.  No love there.  This is the only cell phone company I have seen that doesn't look work with existing customers.  I have called a few times and no one even offered to work with me, they simple tried to convince me that they are the best company (even though the prices and coverage are better with others if I switch).  Shows you what they think of loyalty.  It's really disappointing.  This post reminded me of the frustration I keep having in trying to get a deal from TMO that ISN'T for new customers.