From LivingPianos.

Welcome to LivingPianos.com. I’m Robert Estrin. Today we’re talking about why it’s so important to practice your scales and arpeggios in four octaves. You might think playing scales is just the same thing over and over again. If you can play them in one octave, can’t you just repeat that pattern in another register? It might seem that way, but the reality is more nuanced.
Full Article: https://livingpianos.com/why-you-must-practice-your-scales-and-arpeggios-in-4-octaves/