it depends, a seller is jus gauging the buyers market. on a devils advocate, It what business' do evrytime they release a product, and ask the public what price they feel they would pay. Some people own there cars for a while and do not know the buyers market and prices. il use the mk2 for example people unknowing would think the car is old it must not be worth anything etc, so they gauge the market with a question.
It will always benefit a seller. I say why not ask, there is no harm. at least they know initially how much they will get and whether it is worth selling or holding out.