Footwear is still the main source of animal derived materials in fashion. Leather and suede were once used solely for their durability, but now largely remain a staple due to their familiar look and feel (Oh, and the fact they are intrinsically linked to the meat industry).
Leather is still as common in clothing now as it was a hundred, or even a thousand years ago, but we live in a time where the number of alternative materials available makes its continued use hard to justify.
There are many, many cost effective and durable alternative materials available to manufacturers, including vegan leather, rubber, canvas and more. If people stop buying outdated animal based fashion, then it will stop being made!