It's easy to fill up huge amounts of space with entirely legal content, as others here have pointed out. Photos, home movies, VMware images, iTunes downloads, large datasets, etc. all take up huge amounts of space.

It is. Some people do.

I think more people have a lot of pirated content. I'm not saying thumb drives should be banned, just mentioning the elephant.

My biggest chunk of data is around 300 GiB of photos. Since the raws are around 10–12 MiB each that adds up quickly.