Collect all

Nope. Completely unnecessary.

Collectors take 5 seconds to collect from all of them. This would save 2-3 seconds. In other words: Completely unneeded. If those 2-3 seconds matter so much, you probably shouldn't be playing games.

Additionally, Supercell doesn't want to make the game closer to playing itself, as that would increase the amount of botting (won't discuss that here), and making this automated would only lead into a slippery slope into automating troop production, etc...

Also, I can almost guarantee that the "traps have a rearm button" argument will come up at some point.
-Traps are small, hard to see, hard to tap, and very numerous. Additionally, it requires 2 taps to rearm one,and the graphical difference between armed and unarmed is subtle. Due to traps' size, it is incredibly easy to not see one, which may not be armed.
When I timed myself, it took 30 seconds to find & individually rearm all traps in my base. Thus the need for a rearm all button.

-Collectors, on the other hand, are large, easy to see, and easy to tap. They are not hidden by other buildings, and it is easy to see if they have loot or not. They take 1 tap to collect.
When I timed myself, collecting from all collectors took about 5 seconds.

30 seconds vs 5 seconds. Traps are not collectors. We don't need a collect all button.

Also, make sure to read the stickies and use the search function!