This is a bit like saying "I don't need to learn a new sport because I am athletic and I can learn at the big game!". Sure, you might be able to pick it up faster than the average new player, but a little practise wouldn't hurt to prepare you for the tourney!
Vaccines are literally training/practise for your immune system. Having a strong immune system makes you an ideal candidate for vaccination, because you NEED a strong immune system to get the most value out of vaccination.