Why are the amenities so variable with air-travel

[mattpegher]

I have been doing a bit of flying lately, all with the same carrier. One flight had free movies and games, but you had to buy or bring headphones. One had direct tv, but you had to pay $6 for the 2 hour use (same headphone thing). One had a single movie playing if you wanted to watch. Some times you get free headphones, sometimes you have to buy them.

I can understand that the hardware is different on different planes but the financials seem so arbitrary.