Impedance matching is overrated, the return loss of 50-ohm into 75-ohm is 14 dB, or a VSWR of 1.5:1, it means a low reflection, in practice the return loss is even better due to the loss in the cable. Also, unlike some digital systems that are expected to operate in a controlled environment, Wi-Fi is designed to work with multipath interference, so running Wi-Fi over 75-ohm coax can already get better SNR than running it over-the-air, so matching is not always necessary. You can always add one at the last step if it turned out to be necessary.