We need to talk about the difference between voltage and current and their relationship with resistance.
When you push your power window button the electrons flow through the wires. That electricity makes the motor turn, but also makes heat...
If you don't want to buy one, or don't think something is "worth it", or you think you can build one yourself for cheaper, then go ahead and do it, and allow the person selling these to go about their business—it's pretty simple.