Why the capabilities not added while generating the wpa_ie

[Kiran Kulkarni]

I wanted to ask whether the wpa_ie obtaing from the scanResults bssid 
"properties"
method on the DBus API is generated from the wpa_gen_wpa_ie or which is 
given by the drive.

Also If it is generated from the wpa_gen_wpa_ie then why capabilities 
are not added...
A comment in the code says

/* WPA Capabilities; use defaults, so no need to include it */

So what is the significance of the capabilities...
Also The parsing handled PreAuth only,
what are the other capabilities.