[mediaqueries] Reasoning behind (scan) MQ?

What's the reasoning behind the (scan) media query?  It has two
values, "progressive" and "interlaced", which describe different ways
that TVs (CRTs only?) update their screen.

What's the point of this?  What sort of things would you style
differently based on this value?  Is either value reasonable on modern
TVs or computer monitors?  Can I drop this?

~TJ