I hope that S.o.S. will forgive me developing this a little more...
The behaviour about mature people, retirement and so forth - has built up steadily throughout my generation [Boomer], something Iike a good six decades. To change it will take an almost equally long period of time as the changed attitude has to be built in before people enter work, or in their early experience. We can see how slow it has been for generations to adopt new ways of thinking about many social aspects. Therefore we have to start the change now. Sadly, results not to be seen in my lifetime.
The first time this was brought to my attention was around 1988/89. I was in telecommunications in the City of London. Hiring another engineer, the perfect candidate was in his mid-late 40s about 10/12 years older than me, although I have never looked my age and, at the time could have passed for late 20s.
I knew that he would be ideal for a number of reasons, not least his career in Navy signals. Happily I was proved correct. About six months after he joined my team, we were at a work function and he thanked me for hiring him. I simply said that he had proved me correct. He then said, "When I walked into the interview and saw how young you were - I knew that I would not get the job." That was my first real wake-up call about this problem. I then looked around me and found it to be correct. In my varied working life since then (35+ years in different areas and occupations) I have seen it in many places, not just in the UK.