My rationale behind the issue is this:
I don't consider it wasteful to give away the product, however the resources going into replacing something I already had would be.
For example, I purchased leather Doc Martens about a week before I wised up to the ways of the world and found out how leather was produced. They were already worn in a lot so I couldn't take them back (my ankles knobble together so there was already wearing on the boots after just a week!) and I have teeny little feet (size 2) so there was no one I could give them away too and to give them to charity may mean there's only a CHANCE they'll even SEE another pair of feet.
I digress. While I'm aware there are vegan docs now, even if I WERE to throw out my shoes, I'd be getting them replaced automatically anyway. "THE ENVIRONMENT!" is a pretty solid dot point on the "why should you become vegan?" checklist. So to turn around and throw something out (that has already had the money put back in the industry and giving away won't change) only to replace it straight away and use MORE resources just... Seems... A bit weird and illogical. Not to mention the tapes that will need to be used to break in the new pair.
I keep wearing them and pledge that my next pair will be vegan, when it is necessary to get new shoes. (Even if that means waiting, I have another pair of docs that have lasted me 13 years and are still going!)
Some people however, will give them away because the thought of having dead things on their feet is a bit of a turn off and they don't exactly want to walk around feeling like Ed Gein, and that's totally fine too if that's your way of thinking. Being vegan is meant to make you feel GOOD about yourself!
Hopefully this helps... Sorry... There I go on another rant :3