Retraining only gets you so far - who's gonna hire the 50-year old retrained-but-unexperienced worker over the cheaper younger person, for example?
Not only that, but the older someone gets the more obstacles there are to overcome. Ageism being the first to come to mind, but there might be other problems as well such as work restrictions due to old injuries, poor credit score, previous run ins with the law. All of these add up and can greatly diminish a person's chances of finding new employment. Just by playing the odds game, the older someone gets the more likely they're going to have issues like these happen in their lifetime.
I don't know if this already happened on your side of the Atlantic, but I see more and more fast food chains doing away with people behind the counter for orders, and having instead large touch-screen based ordering. Still don't know if I should cheer that on or not.
The common narrative here in The States is that jobs such as fast food or retail aren't "good jobs." They don't pay well, there's not a lot of room for advancement, the skills learned don't necessarily transfer to other industries, what have you. Therefore their loss shouldn't be mourned. The flip side of that coin is though, those jobs help put food on the table, a roof over your head, and a reason to wake up in the morning. Even if the wages might be inadequate, all of those things are arguably good. If we take those jobs away, replace them with automation, and don't offer any safety nets for the people who've jobs are lost, aren't we essentially robbing the world of the goodness of food, shelter, and purpose?
Additionally, what kind of message do you think the world is sending these people when all it takes is a $200 tablet to threaten their ability to be employed? How do you think they can end up seeing themselves, both as individuals and as members of society?