There are many points, but not least those who want to have long telephoto performance, but can’t afford a 800/5.6 lens, like those who like motor sports, bird lovers, and probably a lot of other uses.
The quality of the images in good light is very close to most APS-C/DX cameras, and you can use the same lenses, with maintained VR and AF.
In low light I switch to my FX camera, but for the rest the CX cameras have taken over, totally.
The DX cameras collect dust, as I see no advantage in using them. The new VR 70-300/4.5-5-6 is superbly sharp, and fits easily in my jacket pocket.
That equals a 200-800/4.5-5.6 on my FX camera, and such a lens would cost at least $30,000, if there was one available on the market. And that would definitely not fit my jacket pockets.
It is also easier to handle if you like to do macro photography, and most of the native lenses are surprisingly sharp, like the 32/1.2, that is just as sharp as the famous Sigma 35/1.4 Art, which I use on my FX camera!
Started out doing photography at the age of 6 using an uncle's old 1940 kodak brownie box camera. At 15 years of age, I decided to buy my very own 1975 Praktica SLR camera. I now shoot with a Nikon D850. I do unpaid TFP and commercial paid work.