You sometimes have to accept they know the risks but see their remaining years as a ‘quality not quantity’ concept I don't accept they know the risks at all, as it is hard to understand for all of us the enormity of the risk. The thing is- if they get sick with Covid-19, they won't just not bother the health-care services and people with a conscience won't leave them, so they are entering the system at the worst time and are making others potentially sick or bumped down the queue to treat them.
The poster who said that you've got a 1/4 chance of dying shocked their parent. It's very easy to say 'oh it's just flu/I've had my time/I'd rather live for now and not worry/if my numbers up' in a general way, but really not so much fun to face distress and death in an NHS without the resources to cope- there is someone on another thread whose FIL is dying of lung cancer and there are not enough resources on the respiratory ward and he is only allowed to see one person a day so is now not saying goodbye to all those who love him.
If they genuinely, knowing the true risks, want to take them, why not spend those final few months directly helping those with Covid-19 then as a hospital volunteer? My 72 year old mum could easily do that, but she's actually sensible and is self-isolating, which means not seeing her grandkids except for a wave when we drop stuff off, not going out for coffee, choir, holidays.
Yes, life is nicer if you go to the shops every day and have a coffee but so what? I don't believe many of these people are choosing quality over quantity at all, they will want both and be very very distressed when we see what has happened in Italy happening here. People don't like change and they do like pottering about doing what they please, but that just isn't going to be possible without affecting someone else, and no, we won't just be able to let them get on with that choice indefinitely if these measures don't work, more dramatic measures (like my MIL in Europe where it is illegal to go out unless to work or for food) will be taken.