If you ask most senior citizens or simply most users of computing devices to explain what they think about "background services", most won't know what you are talking about. Just because a functionality has been present in a system for a while does not mean that everyone will know about it. Ask people about dual booting, most won't know about it. Ask most people about "SSL", most won't know about it. Ask users about the command line, most won't know about it. And so on. Even the abstract concept of a search engine (separate from the concept of Google Search) is likely to fly over the head of many people. You vastly overestimate your audience. Let's put it this way: most computing devices nowadays are mobile phones and for many people this is their first and main interaction with computation. The modern ubiquity of phones is bigger than that of personal computers by an order of magnitude imo. Personal computers were huge but mobile phones have a level of penetration PCs could never reach.
When you buy a device, you agree to the terms of service. Most manufacturers like Apple have something along the lines of "don't interfere with the proper working of the system". Freezing apps sound like it breaks the ToS.
Buying a device is less like buying a toothbrush and more like buying a tractor. You don't own it inconditially. You own it under certain terms. Those terms give the manufacturers lots of power.