New Internet Plans with 5 year Guarentee

I went into my local Xfinity store to change my internet plan to one of the new "all in" plans with the 5 year price guarentee.  I learned at that visit that this is only for NEW customers.  Current LOYAL customers are not eligible.  I mentioned cancelling my service and then signing up again.  With this I was told there has to be a 6 months gap to take advantage.  Why would you not allow current customers to take advantage of this?  My Condo building has only had Xfinity for many years, so it was the only option.  Recently Verizon Fios came in and wired the building for free and are offering us good deals to switch.  Would Xfinity prefer I do this rather than allow a current customer to take advantage of your new pricing plan?  Please explain this to me.  I would rather stick with Xfinity, however, if can't be accomplished, I will make the switch.