I check my mixes on different speakers, for a simple reason: flawless mixes sound astonishingly similar on all kind of different systems. The better the mix, the less the sound is changing in comparison to worse mixes. The reason why mixes are checked in cars, on handys, boomboxes, bluetooth speakers, PAs is to find out, if the mix has a problem. Because if it has a problem, on one of these systems, it will fall apart in comparison to a better mix, while very good mixes never fall apart anywhere.
I think the popularity of the NS-10s or the Auratones, although they have different sound signatures, is, that they have proven to be helpful to get better translating mixes.