Meat eaters. What's preventing you becoming a vegetarian/vegan ?

Especially for older people, it is difficult to meet protein requirements from a non-meat/fish/dairy diet. Very few plant sources provide all the essential amino acids (complete proteins) and to even come close with only plant-based foods requires a lot more calories (one food providing an amino acid absent from or in short supply in another food) .
An 81 year old friend at the gym whom I see doing pull-ups tells me the portein is necessary for his strength training which is essential for healthy senescence. There are some good youtube videos on protein intake and strength training for older folks.