[addaon]

This is an MTA map, not a general “transit” map. Having the AirTrain on it is a bit of a bonus, but probably reflects (a) it being the most common question MTA gets and (b) it being more integrated with the rest of the MTA system than PATH (use of metrocard, etc).

[NoToP]

You can in fact use MetroCard on PATH though.

[addaon]

Today I learned. Shows how often I go to Jersey. Thank you.

[TimK65]

What is this "metrocard" of which you speak?

(It's going away at the end of this year.)