Why most of the LNA/PA output are differiantial pair lines?

Why most of the LNA/PA output are differiantial pair lines? Is there any relation to improve linearity?

Thanks

Surely. You can figure out yourself, if you consider what happens to even order nonlinearities in a differential amplifier.

Apart of this point, achievable output power in a low voltage system (e.g. 3.6 V supplied mobile phone) plays an important role.

Besides reduced even order distortion, is also the susceptibility to common mode noise couplings through the supply rails reduced.
Effect of bondwire inductance can be reduced. Especially for low noise RF CMOS circuits is balanced output a must to reduce noise caused by substrate noise injection.
Some of these advantages in noise and harmonics can easily get lost at balanced-unbalanced transformation on PCB with aid of synthetic transformers (real transformers are too expensive in private consumer electronics).