Three aspects of this occur to me.
The first has to do with MIDI and live performance. The former isn't, the latter is -- live. While it is very nice to have superb recordings, in my humble (yeah, right) there is no substitute for live performance. Now in some live music the absolute quality of the instrument is not that important, particularly if it is heavily amplified (think rock group). In much live music, however, the quality of the instrument is important -- this goes as much for jazz as it does for classical.
Which brings me neatly to the second point, which I approach more from the standpoint of an organist -- which I was for many years -- that a pianist, although the point is valid. I have been acquainted with and had the privilege to play a number of really good digital organs, as well as a number of very good digital pianos. There is a problem common to both: reproduction of the sound. It doesn't matter one bit how good the digital file for the selected note (or notes or stops) is if the sound reproduction equipment isn't adequate. Now some of the instruments which I have played have truly astounding amplifier and speaker systems associated with them, costing many tens of thousands of dollars and taking a good deal of space (a lot bigger than a concert grand) and they still did not capture the sound of the real thing. Very good, surely. Real? No, sorry. There are good reasons to pick a digital organ, of which the best is space (organs do take a lot of space) but price isn't one of them, because of the sound system. Sound reproduction for a piano is very nearly as demanding as that for an organ, except for the extreme bass (below 16 hertz).
The third is actually a rather minor problem, and the best of today's digital pianos have almost overcome it. That is the feel and responsiveness of the action. But... those digital pianos which have that good an action are not cheap. Not as expensive as a top end grand, no. But certainly not cheap!