My question is: What's so special about them? It's hardly fair or ethical to offer jobs to a certain age range and exclude everyone else who might be qualified. Even if it happens to be mowing the grass in a park, there are many who are willing to do that because they need the experience, the money, or both.
There's no denying that younger people do have higher stamina for manual labour, or their skills in a certain field are sharp if they've been studying it recently. However in many cases they lack the wisdom to deal appropriately with the people around them. Being in an actual workplace is not the same as playing a video game simulation.
I've been to multiple job interviews where the question "How is your knowledge of such-and-such" comes up. My truthful answer is that my knowledge might be limited or rusty but I'm willing to learn in order to bring that knowledge up to snuff. Unfortunately that's not the answer that recruiters are looking for; they want people who already know everything about said subject. That way the company won't have to waste time training or wait until the person gets the appropriate education.
What it comes down to is the old "need the job to get experience but need experience to get the job". Sometimes it doesn't matter what age the applicant is.