Do some have a tendency to perform etudes too mechanically: focusing solely on note accuracy, precise articulation, etc.? This is most likely to happen when the etude features unbroken strings of notes (e.g. scales and arpeggios). Many may instinctively approach etudes vertically—note on, note off. The result is static & sterile and just not very expressive or musically satisfying. How can we bring the technical etudes to life? Try changing note durations: some notes longer (tenuto), some notes shorter (staccato). Try modifying dynamics: either becoming louder or becoming softer. Try emphasizing the first and last note of each measure. In arpeggiated passages, emphasize top notes and lighten up on bottom notes (or vice versa). Or, bring out the changing notes and allow the repeating notes to fade into the background. Look for melodic patterns to emphasize. In this example, notice how the changing bottom notes form a melodic line and the top repeating notes function as a kind of accompaniment.
A general rule is “short to long, weak to strong.” But, it ultimately doesn’t help to apply a mechanical method to playing expressively! Once some of the expressive tools & techniques have been exercised, it’s time to make some choices. Where are the phrases? Where is the climax of each phrase? This has been called the “pivot point.” Aim for this point in the phrase by increasing energy (crescendo) and recede from this point by relaxing energy (diminuendo).
Update: a student came in this week and played an etude with the primary goal of playing it musically, but noted that by focusing on playing musically, technique was improved.