Those company which don't charge for service call still have the expense of paying the tech, the truck, etc. So the cost is still there. Either you pay the service call when the problem arises or you pay every month in the form of higher charges. The problem with the higher monthly costs method is that you may never need a service call in your lifetime but each month you pay for all your neighbors' service calls on your bill.
A truck roll typically costs $100+ to the company for even a simple service call. Someone is going to pay for that. No such thing as a free service call, even if the charge for the service call is $0 on your bill. Think about that.