All these colorful elements are prepared for the younger generation of players - who want to stand out from other players to some extent (and are willing to pay for it). So producers/publishers give them this opportunity.
True veterans of the Battlefield series have such things in high regard. If someone wants to parade around like a clown on the map, no one will stop them from doing so, they will be an easier target to shoot when they are driving around in a golden tank with "I love mommy" sticker.
Who cares? If you want a more realistic-looking shooter, just ignore such things.