Why would anyone want a hybrid organ?
It usually comes down to either cost or space. Upgrading with new pipe stops can be prohibitively expensive. Usually the cost of digital stops is about 1/10 to 1/3 the cost of real pipes. For many churches they simply get much more for their money by going digital or they end up simply doing it for less.
The other reason is a lack of space. Adding a new rank of pipes can take up a lot of area. Some venues simply do not have the space. Also, the more ranks, the more space.