It is very common practice for suppliers to provide substantial incentives to get customers to switch from their current providers. That is considered a marketing cost, justified by the revenue that is anticipated from that customer over the course of the minimum period of time that customer is projected to remain with the service (perhaps even assured via the customer making a service commitment). Offering such incentives on a continual basis would take a profitable enterprise and turn it into something that never makes any significant amount of money, as they'd continually be incurring cost instead of earning profit. That's not a viable business model.
Customer loyalty is a very interesting topic. Most customers mistakenly think that continued patronage indicates that they are being loyal. That is not the case. Customer loyalty is indicated by the willingness of a customer to pay a premium for what is being provided. A customer who is only willing to get what they wish via an incentive discount is not loyal.
Here's a good Wall Street Journal article covering this:
Why a Loyal Customer Isn’t Always a Profitable One - WSJ.com
