If only it were that easy. DIRECTV and DISH use completely different satellite dishes, and both use different dishes from the freeview services offered in Europe and in the Caribbean and the satellite services in Latin America. This can cause trouble for people who travel, and also for people who want to enjoy multiple satellite services because there is no one service with every channel they want. Most people don’t want their roofs looking like a dish farm (I guess I’m in the minority there, I think it’s geek chic.)
To the average observer, you’d think, “satellite is satellite is satellite. Why can’t they all use the same dish?” There are two reasons. First and foremost, DIRECTV dishes listen on a frequency different from every other satellite frequency in the world. Pretty much every satellite provider on the planet, including DIRECTV’s own Latin American subsidiaries, use the Ku band from 12 to 18GHz. DIRECTV US is the only licensee in the entire world for broadcasting and reception of the Ka band of 26.5-40GHz for consumer television. The Ka band is wide open and allows a lot higher bandwidth communications. So, long story short no other satellite dish is going to get Ka band broadcasts. DIRECTV also uses the Ku band but only for its standard definition channels.
The other limiting factor is the spacing of the LNBs on the dish’s front arm. Both DIRECTV and DISH operate numerous satellites in numerous locations, which is why you see more than one white-covered LNB on the front of the dish. The spacing of those LNBs is specific to the provider, in order to make sure that a dish pointed at one satellite location will also get reception from every other location. In order to get all the locations at once for every provider, you would need a massive assembly on the front of the dish, and that’s just not good common sense.