Very simple, Michael. 16D technology should have died off about 25 years ago and been replaced by C can motors, but thanks to Parma, it just never went away.
Enter the Retro Hawk, a much improved version of the Falcon 7 with better quality, a tied comm, better bushings, magnets and brushes, and performance on par with a 16D. Given two matching cars, both with the same chassis, body, quality components, with the only difference being the motor, eight times out of ten the Retro Hawk powered car will beat the 16D in a flexi simply because of the lighter weight, and slightly lower center of gravity since it's smaller.
Granted you can buy cheap Pro Slot sealed 16D motors, but you have to go through several to get a good one and overall quality is just not there anymore. Retro Hawks, once properly broken in, either by water method, or on a power supply, are pretty dang equal, and most people can get up to five or six races of a motor with good treatment.
In Florida in the My Series, we had a special tagged American made arm made by Pro Slot, marked FL16D, with fixed 30 degree comm timing. When they first came out, the quality was very, very good, then over the years, the quality got worse and the performance very uneven. Now, you may have to buy 10 arms to get two good ones, but even so, it is 30 year old technology that should have been replaced. For $12.99, you can buy a Retro Hawk, break it in, and go racing, get four to six races out of it, plus some practice, when it loses brakes, buy another one of the shelf , break it in, and put it in the car.
Or you can buy 10 $25.99 Pro Slot armatures to get two good performing ones and hope they last a season, then contend with a car thats 10 grams heavier than the guy next to you that's running a Retro Hawk who is eating you alive in the donut. Not to mention the cost of the items that go with a 16D motor program like a magnet matcher, magnet zapper, can tools, bearing installation tools, diamond hones, comm lathe, etc. You don't have to have a motor program like that.....a simple cheap throw away motor, that doesn't allow tampering and keeps everybody pretty equal is all you need.
This from a guy who had a pretty good 16D and S16D Pro Slot motor program. My box pretty much looked like the picture Danny showed above. Never again.