"This makes it all the more important that we have legislation to force them to make proprietary parts available for riders to buy themselves"
Of course this should be the case, but even then I'm not sure it would help, as they will simply make the spare parts so costly that it's uneconomical.
Maybe there should be a 'standardization' score, somewhat like energy efficiency scores, that could then be mandated.
Or mandate that parts interfaces must be documented and published as standards, and be free and open for competitors.
The basic problem is that almost the whole of business has discovered or decided that their reason for existence is to get money out of people, and that providing the best products and services they can is merely incidental and not actually necessary, especially if they all play the same game.