Non Ghana Citizen Card (Accra)

I traveled last weekend to Volta region,and on my way back to Accra,upon reaching the check point at Sogakope,i was asked of an ID.I presented my Non Ghana Citizen Card,and the officer or whoever he was asked me again of my passport.i did not have it with me,thinking the card will be 'enough' to prove my identity,thus i end up paying 20gh cedis just to continue my trip back to Accra.Now my point is:while doing the non citizen card,u have to present your passport with a valid resident permit,that is a fact,thus i am legally "OK" on Ghana land.so do i really have to carry both my passport and that ID card every time m leaving Accra to another town,just in fear of meeting a officer who will ask me both?what are the use of the resident permit and that card at the end?!