Dear Daniel:
I think there are studies and Studies.
Haha... yes i agree. The big difference is that one group is music, and the other is stuff for you to butcher at your pleasure.
I think that with hanon and czerny, there was a big movement in late classical period, and the early romantic period to try to teach technique using a scientific method. The idea was to start with the basics and build your way up. Sounds logical doesn't it? So lots of composers turned to writing these exercieses, some of them have survived and appear as we see them today. Theses exercises concentrated mainly on what they considered a system to build techinique and did not worry too much about musicality. The two very popular ones have survived and have been mentioned. There are many many others that have just died off over the years.
There are some basic questions with this.
1. Does it work? Can technique really be broken up like that? Learning each bit separately, and almost instantaneously putting it all back together in another piece, where it usually appears in much more advanced forms and expect it to work?
2. Conversly, take for example beethoven's sonata Op. 49 No. 2 which requires scales, can i just learn those (G major?) scales without systematically going through the rest of of these? If you learn scales from czerny school of velocity, do you play the scales in the beethoven in exactly the same way? Are there different requirements in movement and touch for scales appearing in different pieces?
At the moment, my teacher does not make me do any technical exerciese whatsoever. I don't even play scales outside of those in the pieces. What I do notice is that despite this, I do end up playing lots of scales and appegios anyway -- major, minor, stacato, legato, straight up, dotted rhythm, to sound like a harp with a light touch, to sound skippy with a pointed touch, with a deep singing sound, digging into the keys. Not all scales are the same.
With this, my current opinion in line with hers is that you cannot separate movement touch and sound and isolate a particular bit of technique required. Unfortunately, employing a systematic method to teaching technique, without the focus on musicality or a musical context sort of misses the point in the first place -- to learn all these things so that one can play musically. Conversely, if you can already play scales with all these different touches and sounds, rattling off an unmusical set of scales is absolutely no problem. This does not mean I do not do purist exercesies. But only do them in the context of the piece, with a clear final goal in mind.
I use to hear/read that the reason for learning technique is so that it things become automatic. Personally i think this is simply not true. I do the technique so that I can think harder, not less. Much more about the musicality and less about tripping over my own fingers.
I also believe that at the foundation of technique should be your ears, not how fast you can play, or even how accurately. I spend much more time trying to teach my ears (brain) to identify musical sounds and with that the movement and touch to produce them, than playing a set of notes repeatedly.
Doing it from pieces also presumes that you have an excellent teacher that can assess your sound and communicate what you need to do to improve it an an accurate way.