"who don't have the time to retrain"
The reason why we hear and repeat that old people need to retrain, is because employers don't want to hire older people and knowing that very few can afford the time and money to retrain, and that it's politically permissible to discriminate based on "retraining" then you're going to hear a lot about how its really important to retrain and old people need to work harder and its all the victims fault if they won't retrain and much hand wringing about those darn victims bringing it on themselves. If we had a magical (online?) way to retrain old people, the mantra would insta-shift to some other made up reason why old people can't be hired and no one would talk about training anymore.
It the same thing with women or minorities who aren't cultural fits. Its not that there are no star wars fans in those demographics or that it truly matters, its just a way to say in polite company that blacks need not apply because of racism. Just go ahead, "change your culture" and we'll hire you. Oh you say that's impossible, oh so sad I guess we'll hire the white boy instead. What a shame we really wanted to hit our diversity quota, but, (shrugs shoulders) well you know how important culture is. I mean look at how important culture is at every other employer who coincidentally also doesn't hire black people. Oh it doesn't matter in the greater economy? We'll we're special snowflakes in this industry, you see, and you outsiders just don't understand, we really, really don't like women programmers or black programmers.