The perceived minimum track height on my monitor is 3mm (approx.). The next level is 6mm, the next 12mm and so on.
If I have a project with about 20 tracks, at minimum height the tracks occupy just over half the screen. At the next level the bottom tracks disappear downwards and require scrolling to see them.
If there were intermediate levels of zooming beyond those available at present, screen space could be utilised more efficiently.