Why do we do matching only at the interface between the IC and the PCB?

hello,
i was wondering why do we do matching only at the interface between the IC and the PCB , why not inside the IC too, i know that the distances inside the IC is small comparable to the wave length but isn't matching for maximum power transfer, so it shouldn't be about distance but about power transfer.

in IC the distance is samll if compared to the wave length , so the signal is treated as voltage ,
but in large distance which is compared to the wave length the signal must be treated as EM wave travelling along trasnmission line , which characteristics impedance and the termination impedance will create a reflection coffent , and so on

so in large distance u have to deal with ur signal as a wave , but in small distance u deal with it as a voltage and current


khouly

interesting, what about the input and output impedances of circuits in the same chip, for example a LNA and a mixer ?

BTW, the input and output of Power Amp need to be matched to 50ohm to reduce signal reflection

for the power AMP u need to implement a interstage matching between the driver amp , and the power stage
and also u need to do a matching network between the power stage and the load

khouly