@YourBrightOpalSeal
At charitiy shops, you can flounce off whenever you want.
As a volunteer, that's exactly what I do. If I want to take time off, I do. Whenever I want.
the resentment,emotional manipulation and dynamics of taking time off while other volunteers have more work load are still there like in paid jobs.
I'm not sure what you mean by this - are you saying that volunteers who take time off are met with resentment by other volunteers who have an increased workload as a result?
In my experience, volunteers have never, to my knowledge, been resentful of other volunteers taking holiday, and taking time off does not result in an increased workload for the other volunteers. They just do their normal workload. I've never been forced to take on the tasks of volunteers who are on holiday. The work they would do just doesn't get done until they return.
There are volunteers who were let go for not turning up often enough
If that has happened anywhere, then I agree that volunteers shouldn't be let go without the shop trying to work around it first. Charity shops naturally want volunteers who can (normally) commit as much as possible to certain dates and times, but if the volunteer is no longer capable of that, I think the charity should try to see if there is a way to accommodate them first instead of jumping straight to letting them go.