Normal people like to find the things which they store. If they're storing images, 99% of the time there won't be much metadata or text alternatives available — it's the same reason why everyone is investing in image classification and face recognition so you can search for “uncle bob” and find pictures which have them.

Dropbox has never been sold as "pure backup" like Backblaze, and isn't priced like it (I'm a paying customer of both). I'm not paying Dropbox to backup my data, I'm paying them to sync my data across machines, make it available to me on devices I don't own, make it easy to share with family and friends, etc. I want Dropbox to OCR my documents -- I don't really want Backblaze to (and Backblaze's margins probably don't have any wiggle room for added features).

The primary purpose of dropbox was never "backup". It was always to intelligently store and share data, and to be able to identify information inside of it - like if it's an image, have a gallery. If it's a word doc, have a light weight interface for reading and editing, etc. It was also one of the primary ways to get data out of cell phones because of the "sharing" and "syncing" options.

I think you are confusing dropbox for something else?

In fact I think dropbox would be a horrible backup solution! Don't use it for backup or you will be disappointed.