If you bow to someone as a sign of respect, are you worshipping them?
Why are you pulling loose definitions from dictionary websites and applying them to very specific contexts? The only definition that fits anywhere near the idea of saintly veneration is: "a feeling of profound love and admiration." If you're going to claim that any sort of profound love and/or admiration is "worship," then I think perhaps you need to re-examine what worship really means.
veneration*
Given that the Bible is a product of Tradition and is part of it, why is this a problem, again?
It's a prayer. Why do you pray?
veneration*
By the way, it's not vain.
No. Catholicism makes a distinction between saints and Saints. Saints (capital S) are those who the Church has declared, with certainty, to be in heaven. Saints (lowercase S) are those who are in heaven, as well as the believers. Huzzah communion of saints.
It's a prayer. You pray it for the same reason you would pray any other prayer. It has the specific intention of focusing on the life of Jesus, though.