This adulation of speed per se is a very peculiar thing, is it not ? Whole forums exist devoted to that ideal, and their members are not, in the main, musically shallow as might be suspected, but musicians of thought and depth. The phenomenon is, moreover, not constrained to classical players and concert pianists. Idolising speed is rampant in jazz and ragtime, and has always been so to some degree. Contemporary ragtime, in particular, seems besotted by it at present and the effect has caused at least one serious composer I know to eschew the label "ragtime" altogether.
My own view, as it pertains to my improvisation, is that velocity is just a variable option like any other musical property. If it adds to the musical effect then I use it and not otherwise. Its cautionary and very interesting consequence is that it alters the aural effect of rhythm. At very high speed, one cannot perceive much except a flow of notes, which is fine if one desires that outcome. The same is actually true of very low speeds but in a different way. At very high or very low speeds, it becomes difficult to produce those rhythmic events which to me are the soul of piano music. Other musical aspects will be "flattened" at high speed too; a beautiful harmonic change simply won't register in the listening mind if played very rapidly.
The whole issue of fast playing, and velocity in general, is much more complicated, psychologically and musically, than we tend to think, or so it seems to me. Speed as a competitive standard, a purely physical exhibit, a gymnastic achievement, holds no interest for me at all, and it is still a puzzle to me why so many otherwise wonderful musicians persist in embracing it as an end in itself.
Topic: playing fast