That is correct, there are no antennas included for 2.4.
The reason (in my mind anyway) is that there are so many potential roles for that group of devices and so many possible ways to mount it, and so many potential coverage scenarios, that there is no "standard" antenna that they'd want to include.
Shop around and find a couple 2.2dbi rubber duck antennas with reverse TNC connectors (RTNC) and you should be all set.
Good Luck
Scott