I think ARM is trying to get better at it, they are recruiting software people, that won't have much effect on the drivers for the bits of ARM SoCs that they don't design though.
What ARM should be doing is putting it in their license terms to require the makers of the SoCs to do it, where "it" is making the software open source, because that's the overwhelmingly obvious fit for a company in their position. And for that matter for the makers of the SoCs because none of them are going to put the resources in to make the software great by themselves and you don't want to be handing out footguns to every middle manager who can't see that.
