Yes, but it's like when you're at a cafe and need to go to the bathroom so you ask the random guy next to you to watch your laptop. Sure he could steal it, but you reduced the attack vector to just him.
It's a reasonable analogy. To use your analogy I'm suggesting you don't trust anyone with your laptop and bring it to the bathroom with you. If something is truly private and / or valuable information don't put it in the cloud. I'm not alone in that thinking. When it comes to storing people's digital currency you hear about things like cold storage. For very good reason.