So it looks like there are both engineering and marketing reasons today for choosing a double chainring with some applications when they have gone through the trouble of installing a front derailleur and shifter. Thanks Guys? It makes sense to me. And in the past, Maybe they didn't think of it.
Yesterday just when I was convinced I could shift the front derailleur any time in any gear, I discovered why it is suggested we use the rear one instead under load. The chain got hung up somewhere, It took some careful backpedaling to keep from getting it jammed in the frame again. It works good most of the time. This is an inexpensive recent bike, So I guess I shouldn't be too surprised.