Why do you need skateboarding shoes to skateboard?
Well You technically don't but i think they say that because of the gum grip on the bottom of the shoes gets a better grip on the board and also some non-skateboarding shoes tear up faster because they were not made from a certain type of material. Most skateboarding shoes are made up of a gum grip on the bottom and suede leather.
You can skateboard in any shoes but converse are not considered skateboarding shoes. Most Converse shoes are casual like Jack Purcell, Chuck Taylors, etc. However, Converse also has some skateboarding style shoes as well, such as: Volitant, Kiro and Karve Ox, which main purpose was skateboarding, now people use them as casual.
Vans do not give like a magical ability to skateboard, however, they do enable you to keep better balanced and comfort while skateboarding. The inside of the vans, like most skateboarding shoes, have a soft inside that does not rub the skin. The bottom of vans and other skateboarding shoes are flat which also helps the balance of the skater.