Romans knew about thousand based multipliers with a mark over the letter.
Okay, please share your wisdom, tell me how would they express "1,000,000,000 - 100" using Latin numerals?
Oh, I found the answer on my own, with the help of LLM. For a billion you can use M̅M̅, which technically would mean a thousand thousand thousands, and to denote the calculation above you'd write - M̅M̅CM. But my point still remains relevant - this is the modern extended version of Roman numerals. In ancient Rome they typically never would go up to a billion.
Now imagine trying to explain to them the concept of subtracting a hundred from a billion and the most straightforward way to deal with that is a decimal numbering system. I think they'd kill you for blackmagicfuckery on the spot.
Well, if that comparison feels condescending, let's imagine ancient Romans - with all their sophisticated culture, economy and traditions. They wouldn't kill you, but still the idea of a number such a billion would probably terrify them. They'd probably be like: "dear sapientissime señore, we respect your wisdom, but we rather use... Lua"