” Now the conversion is no longer done, and they leave the engineers to do it the way that has always worked”
Yep, we all know that the metric system was not born out of necessity or by scientists. It was born out of politics and still is.
Oh for heaven sakes. You claim to be a scientist, not an engineer, not a computer programmer, who uses the English system. And, you claim the SI system is political, despite the fact that it is simpler to use. You also claim that SI is "arbitrary." Well, in some sense, all measurement systems are.
As has been said, the meter was originally defined as a fraction of the distance between the pole and the equator. It was not redefined because the scientists were stupid. It was redefined to make the standard easier to use.
In the same way, the nautical mile is not defined as a distance. It is based on angular measure. It's the distance that one angular minute of longitude subtends on the earth's surface. That's why it is convenient for navigation. But, if the meter is no good because the earth is not a perfect sphere the same problem would apply to the nautical mile.
And to the rest of you, a Kilogram is a unit of MASS and alway, alway, always has been. You can compare it to other masses with a balance, as has been said before. A balance does not measure weight. Weight is measured by a spring scale. Or, you can measure mass with something called an inertial balance. This is basically a spring system that oscillates at different frequencies depending on what MASS is put on it. 9th graders learn the difference between mass and weight in physics class. If you don't know, please don't embarrass yourselves by debating a point that is not debatable.
In the same way, the SI system is not debatable. It is one of several measurement systems that is in wide agreement. All measurement systems are arbitrary in their fundamental definitions. But the SI, and related systems, are decimal. So, it is much easier to use and much less likely to cause errors than using "pounds mass" or "pounds weight" or "slugs" because these are confusing by their nature. Would you claim that British pounds, pence and farthings were superior to 100 pennies to the dollar? Even when engineers work in inches, they now divide the inch into tenths, hundredths and thousandths, not eighths and sixteenths.
There are other measurement systems in use that work well in their domain and scientists may mix systems a bit for convenience. You wouldn't expect an astronomer to measure in microns or an atomic physicist to measure in light-years. Navigation, surveying or other disciplines may use other systems but that doesn't make those systems universally superior in some way. Bushels may be a convenient unit for an agricultural scientist. But to claim SI is based on nothing and a political plot is extraordinarily narrow minded.