Unless you live alone I don’t get why you can’t cope a bit longer without meeting people!
Theres a lot of reasons. Each of them valid. Just because yu have decided its too large a risk for your parents, does not mean someone else will come to that conclusion, and thats fine of course. Both would be 'right' IMO.
Everyone will assess their personal circumstances and decide accordingly. Which is how it should be really.
And those worried about getting ill/giving it to others in the meantime? Stay in if you want.
If it starts getting too overboard, 'rules' will be changed. But for now, some normality is a godsend tbh.