Well, digital camera is different. There is some menu with just a few items and every item has just a few options.
On the other hand, in transmitter you often set values -150..+150 %. That's a lot of click, click, click, click, click, click, click, click, click, click, click, ...
Sure, you can push and hold. a) it does not speed up = takes too long, b) it does speed up = you are going to overshot (with bad acceleration value, you can overshot several times). With rotational encoder, you are not waiting (getting the "everything takes too long" feeling), you are active (in control) and given you can rotate it with different speeds (different increment), you don't have to click (rotate) like crazy.
So I prefer rotation encoder, but I can live with buttons too. Best option - rotating ring (no push) with push button in the middle (no rotation).
It seems, that to make as all happy, FrSky has to put touch screen on X16D, but with sw that allows to configure everything without touching the screen. Just using standard buttons or encoder - with both of them present.
I guess not everyone will be happy