As said, scope displays tend to follow the trend for other applications, for cost reasons to begin with. These days, a decent 16:9/16:10 IPS panel can be had for pretty cheap, whereas for a different form factor you will usually have to settle for "industrial" displays which can be VERY expensive. Back in the old CRT days, wide screens were very uncommon and would have been very expensive. So that's the cost factor.
As to usability, it really depends on your use case. If you're typically often capturing "digital" signals and want to analyze a significant portion of them, a wide screen will be better obviously. You'll appreciate having more horizontally, and won't care as much for amplitudes. But you may also want to analyze signals where amplitude matters more, and then you'll appreciate having more vertically.
Of course for specific uses, you can always either use some kind of USB scope, or just grab the samples from your scope and display them on a computer screen.