I'm sorry, instead of:

> it wouldn't provide much value to the vast majority of customers

I should have phrased it as:

> it wouldn't provide enough value to their customers to create meaningful value for the company.

You can argue that "ha ha, we shall enact regulation to force them to do this!" but the reality is that only a small percentage of customers would actually benefit from such regulation. Because most people are not going to tinker with their devices, especially if there is no easy or straightforward way to do so.

So in the end, you'd have more regulation that makes it harder for new players to enter the market, while doing little to solve actual customer problems and ultimately imposing significant costs on manufacturers.

For people who actually care about long-term device support, they can choose reputable manufacturers that already offer it. If no such manufacturers exist, that may instead represent an opportunity for someone to build a business around providing better long-term support.