Well, the ones we can see are! They're very very very distant objects that are very very bright, but they mostly emit along their axes. So, we can only detect the ones that are pointing at us.
Hmm. If the only ones that we can see are pointing at us then it seems really unspooky that we should be able to look at quasars that are very far apart and see that they all appear to have the same orientation. The ones which have any other orientation are being filtered out. I'm guessing the astronomers must have somehow accounted for this though? Seems like if all of the quasars really were aligned then there would appear to be a lot more quasars when observing in a direction which was parallel to the common direction along which they emit light.
This is not an observation of axes visible from Earth (since that is obviously biased):
The team could not see the rotation axes or the jets of the quasars directly. Instead they measured the polarisation of the light from each quasar and, for 19 of them, found a significantly polarised signal.
Even if it had been the case that they were directly observing axes visible from Earth, those wouldn't appear to be parallel unless they were also proximate in the sky.