What if the file you want isn't on the memory stick you brought? That's the big issue with memory sticks vs cloud storage. Yes, you need internet access (although not if you've already got the file cached, which I've done many times), but at least with cloud storage, you can access ANYTHING that is on your computer, even if you hadn't anticipated needing it.
Is cloud storage perfect? No, but it certainly has a lot more uses than a memory stick. You can backup your entire hard drive, access it anywhere there's an internet connection, share and collaborate with anyone anywhere. You can even use it to sync different computers, contacts etc. A memory stick is good for basically transferring files from one computer to another, and that's about it. It's not big enough to be a backup, you need to be in physical contact with someone to share the file, which happens less and less in todays world.