phone companies have a different idea of 'night'?

I remember back when the phone companies said 7pm was night.. what is this crap? so far i've read that each market has a different "night" start.. how lame is that? anyway this is what the phone companies think 'night' is in the NYC area..

Verizon
Night & Weekend Minutes
Night Hrs: (M–F) 9:01 p.m.–5:59 a.m.
Wknd Hrs: 12:00 a.m. Sat.–11:59 p.m. Sun.

Sprint
After looking it up, Sprint is Basic at 9pm, or Talk at 7pm, with the option to pay more to get 'nights' starting later. what is this crap?

AT&T
Unlimited weekday minutes from 9pm to 6am and unlimited minutes on weekends, with the option to buy 'night' starting at 7pm. again.. what is this crap?