There is no justification for 65+ to pay less than other people these days. It's about time the prices were brought inline (although adult prices should be going down, not 65+ going up). They should keep the discount for 75+ and increase the age each year. 65 year olds are one of the wealthiest generations and the only age group wealthier are 55+ who are following them and will be getting their discount in the near future.
It's a form of low admin means testing but it's way out of step with reality now. Working age adults, particularly those on low incomes with kids are the ones that need the discount.
Before someone says there are poor pensioners that rely on the discount then of course there are but there are on average more people that are poor and can't afford tickets in the adult category. Adults are more likely to be paying for kids tickets as well.