I totally get what you're saying and I agree with you 100%.
Some years ago, in between doing paid jobs for other companies, I worked for various charities as a shop manager/assistant manager/supervisor and I trained volunteers with special needs and the disabled and elderly, the amount of scrounging that went on with a lot of volunteers was awful, they were basically stealing donated goods.
One of my volunteers was an ex-charity shop manager herself, she managed that shop before I took over, then she became a volunteer at the same shop. She was obsessed with bathroom things so as soon as any beauty stuff and shampoo, decent bathroom mats and towels etc. was donated she literally lifted the lot and put it in her own bags. From what she told me she ''had a bathroom overflowing'' with such things.
Another in another shop was obsessed with Mills & Boon books, we put them on sale for only 30p each paperback and 40p hardback. Before we managed to get them out of her hands to price and put them out for sale, she'd snatch the lot then read through them and scribble out any sexual words/phrases in black ink but she loudly announced she hates any sort of porn, she'd damage them by blotting out and she'd sit there reading them all the time instead of volunteering so of course because they were damaged I couldn't sell them. She also volunteered with the shop directly next door and did the same there, but for some reason they worshipped her so let her get away with it while I gave her a mouthful and told her I'll have her done and sacked for theft if I ever see her do such things again AND she'll have to pay our shop full price for each item, as I threatened with the ''bathroom'' lady, reminding them both that those who were kind enough to donate things weren't donating to the staff for their own personal use, it was for the charities, so because of their arrogance, selfishness and thieving, the charities weren't getting the money and the customers weren't getting goods.
There were various other incidents too over the years.
Those sort don't go to volunteer, they just go to scrounge and scavenge and steal.
We had what we called ''sin bins'' in our staff quarters where if an item donated was a bit too damaged to sell, no matter what the item was, then it would be ''sinned'' and volunteers could help themselves to what they wanted as long as it was bought up in front of the manager/whoever was in charge at the time and the manager would then put it through the till as a staff discount.