It's a matter of choice, preference and application. Probably a bit of history thrown in as well.
While it works perfectly well to set the mid-stick pitch to hover when, it means learning another stick position and fell when converting to +ve/-ve pitch flying as used in aerobatic flying and 3D.
When you go inverted then you'll be wanting as much -ve pitch available as +ve.
Consequently, if you think you're learning curve is heading towards sport, aerobatic or 3D flying then it's best to set your mid-stick pitch to 0°.
Autorotation makes a little more sense when set to 0° also, not that I'm any good at autos
If you're going to flyscale then hover pitch may suit you better.
Another approach is in the thinking involved. If you're set to 0° then you Know what pitch you're applying at a given time +ve or -ve.