Ofcourse there is a market for Direct admin , there are hosting companies which are still offering direct admin based shared hosting.
However since cpanel is more user friendly with unique feature its being widely used.
We haven't used it in years. I'm sure there is still a market for it however anything you can have auto setup for a customer you should be able to sell. Granted most people in North America we find like Cpanel, Plesk is starting to grow a bit here however it's not close to Cpanel on this side of the world.
I consider DA as a very good hosting control panel, clean and easy to setup / use on a daily basis up to this date. I know many would say "cPanel only.." but here is a gain the point to consider, if you are looking to host some web sites or even offer reseller packages to allow some one sell hosting accounts, in both cases DA offers much and beyond your needs, it simply does the job. From my experience, it is pretty stable and don't have any special issues if compare it to other popular solutions (plesk, cpanel...). Some people, like a lot the extra mile features and dozens of plugins available for cPanel/WHM, well for those people cPanel would be probably the better choice. However, if you are looking into hosting couple of web sites or offering reseller services, I can't see how DA would be missing anything of what you are actually looking to get. So, up to me? DA would still be an easy to use, clean and a neat choice.
We use DirectAdmin and find it very easy to extend.
Almost every function you can perform as a pre and post script hook, so you can extend the panel very easily, even if you are just using bash or python.
Also the way it handles all domains as equal, rather than the main domain and "add-on" domains is far superior.
I would say that to a person who has never used cPanel, DirectAdmin is easier to get to grips with. It's just like when MS Office changed to ribbon. Those who had never used it previously had no issues, only those who had learnt where everything was had to relearn.
As to the cost, once you have NOC pricing, as we have, you will find that it's much cheaper than cPanel. Lifetime VPS licenses < $90 or $5 a month, which is quite attractive.
Sadly however, I have to agree that we would have many more customers if we used cPanel, but would we be able to do all the fancy stuff behind the scenes? Questionable.
As others have said, there is a market for DirectAdmin.
However, I just noticied that the pricing (from their website) is surprisingly high for the features offered. I think resellers have better pricing which allows them to sell it for a low price internally.