To be fair there is a vast difference in being able to tie knots and needing to tie knots. I'm an SPSA qualified climbing instructor and an RYA Level three dingy sailor and so have a pretty good knowledge of knots and their uses but I still choose to use bungee's for my basha.
Almost in the same way that I'm quite capable of climbing safely without any metal work whatsoever, I can use an Italian hitch for belaying/abseiling etc, I can tie on instead of clipping into things, I can tie turks heads and use them as gear chocks and so the list goes on....however, for ease and speed I use stitch plates, fig8's, nuts, tricams and friends etc..... it's the same for bungee's, I use them for speed and ease.
Having started using basha's in the cadets (where it was a poncho and used as a waterproof) and then used them the whole time I was in the TA I think there's an awful lot in what Gary says about the military using them for speedy bug-outs and I think that and the fact that it's "how I've always done it" is a lot of the reason why I use them.
I'm not anti cordage on basha's, I just choose to use bungee's.
Each to their own though! :super: