While we live in an era of 4K and 8K streaming, the was the "Golden Ratio" for the portable lifestyle for nearly a decade.
Early smartphones and portable media players (like the iPod Touch or early Samsung Galaxies) could decode 720p video smoothly, whereas 1080p often caused lag or rapid battery drain.
The H.264 codec became the standard, allowing "Don Juan" to look theatrical even on a small screen.