Really depends on the airline. Lufthansa will rarely send you on a bus. But the answer is because they don’t have enough gates for all the planes.

Mind explaining? I dont get it (genuinly)

Dont know if you’re only referrung to lobsters or all animals but strictly speaking, humans are also animals and letting everyone live life as they see fit is already the default if you will. That includes letting people who want to cook lobsters do that