AOTW, not all of us are mobile phone savvy or even own a phone that can do that stuff. Access to a computer while traveling is not always that easy either
There is the option of telephoning the briefing office and lodging a basic plan for the CTA segment.
From my understanding of ATC actions/processing of popups -
An ATC is providing separation and arranging sequencing to a bunch of aircraft in his/her sector, arranging STARs, coordinating with other sectors etc. etc. and a VFR NOSAR no details calls up seeking a clearance.
Who is the ATC going give priority to attention-wise?
- The ATC will most likely have worked out a sequence for the other aircraft, which the popup may affect;
- The popup's requested track may require coordination with and agreement by a following sector or Tower;
- The ATC will have to enter basic flight details into Eurocat so the popup can be processed and handed off, so some to-ing and fro-ing radio contact will be necessary to obtain these details.
All this takes time and diverts the ATC's attention.
A flight plan already filed in the system eliminates one distracting and time consuming factor, and assists greatly to facilitate a clearance
