Some large operations take a significant amount of time. If a button is clicked by accident there is no way to cancel the operation.

E.g. I accidentally moved my entire inbox to trash when I thought I was in the spam folder. There was then no way to easily restore emails so I had to move to archive, and then go through each page to move emails back to inbox.

Had I been able to cancel the operation, this wouldn't have taken to long to recover from.