Why would Verizon force me to switch carriers?

I have been with Verizon for 15 years. I have 8 lines and they want me to add another to get a deal. This is ridiculous. I am sure that AT&T or Sprint would love to have my 8 lines of service and offer me a much better deal to prove it. Verizon might be the biggest but they also care about existing customers the least it seems. Way to blow it Verizon. 

Re: Why would Verizon force me to switch carriers?
Customer Service Rep

We most definitely appreciate your loyalty over the years, Drand98, and we would be saddened to see you switch outside the family.Thanks for bringing this to our attention. How many lines were you going to upgrade? What specific device were you wanting to upgrade in to?  JoeyM_VZW