A statistical analysis of customer experience. Make it extremely tedious and difficult to cancel/downgrade/do anything with your service. The benefit of people giving up and accepting unnecessary fees or undesired services outweighs the cost of those that do leave.
Comcast has determined that their strategy of impossible customer service benefits the bottom line more than being a customer-friendly company.
Comcast strategy example:
To cancel a service you must be on hold and bounced between representatives for at least 30 minutes. The percent that give up and accept whatever fee is more profitable than correcting the percent that do quit/give the company a bad reputation.