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.
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.