I suspect it’s a couple things. First, the skill gap - maybe someone begins needing assistive tech and has no idea how to start making. Second, perspective - as an able-bodied techy, I lack the understanding of the problem to build the right thing. Third, communication - can the one in need describe their need? This really requires reflection, and maybe skill. And lastly: money - how many of is can afford to work for months or years on a project that doesn’t (and likely won’t) pay?