LB vanities never came back. LB pets came back because there are people collecting them. One of the objective of having pets is to collect them all. You can't make 3 eggs and put the whole community to fight over them. There must be more. That's why StS introduced the pet crates and they brought back Nightshade and SnS. I still have no idea why they brought back some vanities... Maybe because they were very wanted by players and they tried putting them back so they can have an idea on how things would go. Expect all pets to come back during their respective seasons. Even the old discontinued pets are available through some crafted old locked crates of the watch.