Well, yes, that's kinda the whole question of accessibility. The proportion of people who e.g. can't distinguish colors or use the stairs might be a rounding er

Well, yes, that's kinda the whole question of accessibility. The proportion of people who e.g. can't distinguish colors or use the stairs might be a rounding error in some populations. We still find it valuable to strive to serve them. Some of this has been expressed and thus calcified into regulations.