That's a fair point. I think the problem is that lights tend to just clip onto the handlebars, unlike car headlights which are carefully designed and positioned on the vehicle by the manufacturer. But short of selling bikes with integrated lights - which would substantially increase the price and thus the steal-ability - it's not clear to me how you could solve this.
Yes, true. Mine are dynamo lights so are fixed - I think it'd help if more bikes were sold with these, which are very suitable for urban hybrids. They aren't very nickable as they aren't any use on their own. But I think awareness would also help - I don't think every cyclist is actually aware they are blinding people, much like a car driver with a misaligned headlamp often has no idea unless the police stop them and tell them, at least until it fails the MoT (which could take 3 years if it's a new vehicle with a manufacturing defect). It would also help if they came with a thumb trigger to dim them a bit - the Lezyne ones I used to have do have a dim-bright mode but it's awkward to set it while riding.