Impact of coupling variation (of Hybrid coupler) in communication system

Hello All

I have tried to design few couplers/dividers and have also browsed some datasheets (for example one here:http://e-meca.com/rf-directional-cou...D=1&SpecsID=11).
I have noticed that there is always some mismatch in coupling and error in phase. That is, a 3dB coupler is not 3dB but, say 3±0.5dB. Similarly, the phase difference is not 90° but 90°±3°.
I just wonder ,wouldn't this devation from the ideal values have detrimental effects in the whole communication system chain? If yes, how do engineers cope up with this variation? how do they correct it?

Thanks in advance.