That's because people eat a lot of chicken and eggs, and don't each much salmon. When deciding what to eat, the amount per serving is what matters, not how much of it the average person eats. And again, arachidonic acid is just one omega 6 PUFA, being specifically singled out for promotion by vegans because it is found in meat. The rest of the omega 6s are all just as bad, and our intake is almost entirely from vegetable oil. A serving of chicken has less than 2g of omega 6s in total. That's less than of the omega 6s in a serving of tofu.