Is their product actually competitive? I had tried it once long ago, but currently I don't see any particular niche where it'd be superior to dropbox/google drive/onedrive/whatever.
applications / companies that have security requirements, e.g. healthcare needs BAAs to be signed and Box will do that whereas the rest (of the big players) generally do not
The question is also how does it compare to an on site system. Most large enterprises have invested lots of money in storage systems that are a technically trivial but essential to the business.
Sharing files outside of a company is useful and often problematic. But ironically a lot of large enterprises will block sites like box. Having an ftp style system on your own network is faster to upload and less likely to be blocked by the receiving party.