I had not seen this previously but will be happy to answer:
I use DBF/CDX. However, my reasons are very specific. Let me explain:
I have been building one primary ( for sale ) application over the past 44 years, and I have used DBF files. I started with the very earliest version of dBase, progressed through all versions, into Clipper, then FW, and now Harbour. I found the tools I used were very effective with DBF files, and performance was quite good for my clients.
I considered SQL, and even did some experimentation. However, there were some very key reasons I did not make a switch:
1). My clients were happy with the program, it was rock solid, and they had no interest in how the data was stored.
2). Sometimes files can be corrupted. There are tools to fix individual DBF files and I couldn't find any to do the same on SQL databases.
3). Sometimes a file couldn't be fixed. I have 200 total in my application. If only one is damaged, I can role it back to a previous backup of that file, and then only that one file needed to have newer records input. In my experience, it was usually a counter file or some other small one that could be updated in a matter of minutes. I included an editor for them to do that, although if a larger file ( ie. parts ) had to be reverted a day or two, they could quickly see what was missing and insert it. It's a method that was highly effective. With SQL the whole table would have to be rolled back to a previous date and all that data re-entered ( or at least when I made the decision ).
4). Due to my age, I really didn't want to embark on a lot of time revising all my code to use SQL. As a "senior citizen", priorities change and I wasn't interested in competing against sales teams and marketing falsehoods to gain new clients. Most of my clients have been with me for over 30 years, and they value the fact I answer their calls and handle all of their questions and issues quickly. As they retire, they sell their business to a larger corporation with its own system, or simply close the shop. Family is far too important to take time away to reprogram to a different database. That is just my reality.
5). Advantage Data Base Server was a very effective solution for fast networking and my clients with many workstations purchased that option. Of course SAAS bought it out, and like so many great technologies, they killed it. Having been in this industry since 1982, I have seen so many good technologies discarded to enrich certain companies by eliminating competition with their lesser quality products.
Survey numbers are nice, but they mean little unless they are viewed with the actual reasons. My using DBF doesn't mean it's better than alternatives. It just means it fit my needs, expertise, and future directions better.