Isn't age also a factor?

What's "regular old high protein food"? Do you mean something like meat every meal? When I recorded my meals I found my protein intake to be quite low (I don't eat meat. I eat fish but not every day.).

Age is a factor and goals are a factor, the 1g/lb number is for optimal gains from bodybuilding not the minimum you need to just be alive or healthy

and yeah people who say that protein is easy to get assume that you're eating meat with every meal

on a vegetarian diet you get it from random sources, bread has a little, cheese has a little, it all adds up to the point where you're basically fine especially if you try to include a main protein/meat replacement in every meal (tofu, seitan, chickpeas) but I'm just not a big person and the amount of food I'd need to eat to reach the optimal grams/lb would be too much without supplementation

The recommended minimum is 1.2 g/kg (0.55g/lb)

As I understand it you need more protein as you get older.

I'm curious how, historically, people have fared, as meat has not been as available as it is now (though this has probably varied considerably over time)

Historically older people lose a lot of muscle mass, which also means they gain weight and lose mobility, some even needing assistance doing basic things like walking or getting out of their chair.

Getting enough protein and exercising is crucial as you age, and it's something a lot of people have historically not understood, since as your metabolism slows, you get less hungry right when your protein needs are increasing.