SI doesn't prescribe that you have to use a single unit for all measurements. Are distance in meters or kilometers? Weights in kilograms or grams?
I assume you always just use the base units? kg, m, s, etc.? (I always think it odd that kilogram is the base.) I feel like could get weighty for some applications of a different scales when milligrams, millimeters, kilometers, days, etc. could be clearer. And even if you use "standard" units, if you aren't clear about what standard you use and what that makes that units, people won't always guess the correct option.