Does any other manufacturer produce their own? I think the major issue is that other companies are integrators of cheapest bids for components, not computer companies.
Apple isn't producing all of the components in their laptops either.
It's a bigger picture thing. Apple has some vision for what a good laptop is like, and has been iterating for decades to achieve that. Each new generation brings some amount of change (including some real failures like the Touch Bar and butterfly keyboard).
Absolutely any other manufacturer could achieve that if they were willing to focus on it, iterate, and not give up. It would take some time, but it would happen.
