It’s all about convenience. If you store files on ‘the cloud’ (which is just a server someone else owns), you can access the files from anywhere you have internet. It’s pretty much the same as if you emailed the files to yourself, you can re-download them anywhere you want. Also, you don’t have to have your own large amounts of storage yourself.
However, I fail to see the point in it outside of work/sharing files with other people. I have no reason to put anything private or sensitive under someone else’s control. Not a good idea. I’ve heard stories about some cloud servers mentioning in their ToS that they have the right to your files and anything contained in them.
I had security drummed into me as a kid in the army (AR 380-5). I understand the convenience part, which is why I find it convenient to buy those little memory sticks. I own several, and can take data anywhere I want. I just do not understand todays crowd, not caring what they give to someone else to store for them, or what they say on places like Facebook or email for that matter.