The most obvious use of the word vegan is the act of someone who extends the concept of vegetarianism to include the avoidance of dairy products, eggs and fish. Some will avoid honey. The follow on is the avoidance of the use of animal products for clothing such as leather, wool and silk.
So here we go the avoidance of the use of animals has no bounds.
Each actor will stretch the concept to the degree they can sustain. The continuing use of leather shoes bought before the onslaught of the vegan styling. Some may buy second hand animal products with the notion that that they are not encouraging adding to animal use.
The concept of animal use is paramount as what was a use has become abuse. The breeding of animals for the sole purpose of human exploitation. Old leather doesn't come into that arena but it may be interpreted as promoting the benefits of leather, the reliance on the past abuse or even a provocation to vegans and non-vegans to enter this discussion.