The reason is mostly aesthetic. There's so much going on there already that a second number--and an approximate one at that--seems like more mess than usefulness.
Personally, I just assume that a turn is five minutes and you'll get a reasonable, if conservative, estimate pretty easily.
I can't imagine that being hard- as long as it could find the duration of your turns it could easily just divide each one and display it in Erich's suggested format.