For most people, they just want a computer/games console/cellphone that works, and operates in the way they want it to. Whether the source code is free or not is completely irrelevant, if it fulfils the purpose.
If I buy a plastic toy for my kids, I don't feel the need to have the schematics, plastic moulds, and full assembly details for it. It's enough that it fulfils the purpose for which it was made.
Personally, I think you have to trust other people at some point. You have to trust that a hot wheels toy car won't have a secret hidden camera transmitting back to the government, just like you have to trust closed source software.