It isn't popular for all the reasons stated above. On our Africa trip a few years ago, the three of us had a .35 Whelen, a .338-06 and a .358 Win. They all worked just fine on all the plains game we shot, including blue wildebeest, hartebeest, zebra, kudu, nyala, waterbuck, etc. One shot kills all. 225 gr partitions in all.
OFS!
None of those are popular, either.
They worked insanely well, though. I believe the .338 Federal would have worked just as well, or better.