> is only an issue if there are actual vitamin deficiencies that matter.
It's an issue because it's wasteful, you're loosing the good stuff in the process. Throwing half of your meal into garbage every time is only an issue if you're still hungry afterwards, but it's not economically and ecologically sane thing to do. This is a similar thing, one should try to maximize the use of food that they pay for.
Cooking meat allows your digestive system to ingest more proteins, for example.
This is why fire was such an unprecedented step in our evolution.
For example:
Raw egg: 3g of protein at most.
Cooked egg: 6g of protein.
It's an issue because it's wasteful, you're loosing the good stuff in the process. Throwing half of your meal into garbage every time is only an issue if you're still hungry afterwards, but it's not economically and ecologically sane thing to do. This is a similar thing, one should try to maximize the use of food that they pay for.