You make a great case for an absolutely locked-down device, especially given that it's something that's bristling with microphones/cameras/accelerometers/GPS and logged into the most sensitive services in your life. The market agrees with this stance - Google offers sideloading, and vast armies of people are lining up to never use it. Apple's locked-down product is so successful with consumers that we're complaining about their monopoly power.
You can buy a general-purpose computer for cheaper than a cell phone. The fact that people choose the locked-down pocket computer over the general-purpose device tells me that the locked-down experience is the one the mass market prefers.
The people who I hear complaining about this aren't the regular users, they're the companies who aren't making the maximum profit they feel they're entitled to.