Discriminatory payments

There has been a lot of talk that the mobility allowance scheme was discriminatory as only people below 66 could apply.

I haven’t seen it mentioned that people under 66 can’t apply for the Old Age Pension, which is at a higher rate to working-age disability payment schemes. Nor that people over 80 get a top-up of €10 a week.

Why aren’t they considered discriminatory? In such a scenario, it seems reasonable that extra targeted supports could exist for some people with disabilities of working age.