Efficacy also plays a role.
Adapting existing products, like retrofitting buildings with ramps, is more difficult than universally designing these products in the first place. From an economic standpoint, companies benefit from building in access from the outset. Retrofitting software and curricula for access is more expensive than building it in initially. Employing universal design principles can also increase companies' market shares because their products serve a broader audience. From a legal perspective, universal design for learning is in keeping with the Americans with Disabilities Act.