the character impendance of strip in the cellalur phone?

why do the character impendance of strip in the cellalur phone be difined to 50ohm, but 75ohm in digital TV?

maybe EM energy in digital is higher than in cullular phone?!

50ohm and 75ohm standards are definded by coaxial background. In coaxial cable when Zc=75ohm there are minimum insertion loss. Maximum transmited power can be achived when coaxial Zc is about 33ohm. 50ohm system is compromise between minimum insertion loss and maximum power.
In TV cable systems we don't have big power, so minimum loss is important. That's why in TV cable systems coaxials Zc=75Ohm.