Yes, probably they should. Certainly the over-65s should, and the older you get, the stronger the case for limiting interaction becomes.
This isn't a matter of discrimination. It isn't about the fact that you don't think that 60 (or 70 or 80) is old. It's not about you being very fit when you're 75 or being able to jog when you are 80. It's about your biology and you can't do anything about it.
The older you are, the more likely you are to have co-morbidities. Maybe you don't even know about them. Even if you think that you are in perfect health, you are much more likely than a young person to have an undiagnosed health condition. This may put you at greater risk. But the big, inescapable fact is that your immune system is as old as you are. The older you get, the less effective it is. The less effective it is, the more likely it is that, if you catch it, the virus will invade your organs and you will die.
So do your best to avoid catching it.
Even if you are ready to die at some point soon, and you are prepared to expire alone on a ventilator, what about your loved ones? If you have a spouse, will you risk passing it to them and killing them too? If you have children and grandchildren, are you ready to leave them? Do you want them to grieve, because you weren't prepared to limit your life for a while? And what about the burden on the NHS? And the risk to the medical staff? Do you want to add to that?
I think that anyone who can stay inside should stay inside. If you won't do it for yourself, then do it for other people.