When almost every Japanese person still has to count each unit for large numbers to figure out how to correctly read them, I get the feeling it isn't as easy as you say it is, seeing as they are generally written in the English 10^3 format but read in the Japanese 10^4 format.
You say this as if we didn't have to count our digits to figure out if 8000000000000 is eight hundred billions, eight trillions, or eighty trillions. It's precisely why we have thousands separators, and the only reason the Japanese use them (instead of "ten thousands separators"), is because of Western influence.
Have you ever met those entitled assholes who would visit a foreign country and then complain that "these locals should learn English already"? I've met quite a few of them. Now imagine how they'd behave if they had to pay JPY 1'0000 for something only to later realize those are 10 thousand yen, not just 1 thousand.
If it weren't for the West, the Japanese would have absolutely no problem writing 8 billion as 80'0000'0000. After all:
8万 => 8'0000
8億 => 8'0000'0000
8兆 => 8'0000'0000'0000
8京 => 8'0000'0000'0000'0000
It's really no different from us with our:
8 thousand => 8'000
8 million => 8'000'000
8 billion => 8'000'000'000
You think a new unit for 10 000 and another for 100 000 000 is confusing? Wait until you learn that English has a new unit for every multiple of 10 from 20 to 90, as well as a new unit for every number from 11 to 19. Imagine if we could just say "2 ten" instead of "twenty", just like we say "2 hundred" instead of "twindred". Or if we could say "ten 2" instead of "twelve", like we say "twenty 2" instead of "twotwenny". That said, I don't see how "ninety" is any less confusing than the French "four-twenty-ten". At the end of the day, they're both unique names for a number that should've been "9 ten" from the start.
If you really want confusing numbers, look at German. They spell 21 as "one-and-twenty". Imagine having to take notes on the phone, being told "1 thousand 2 hundred 4 and 30", and hesitating every single time after the "hundred" because you're not sure if that "four" is a 40 or not. In a way, it's actually better than English, because at least in German you always expect this. In English, you hear a "nine", expect "ninety", but get "nineteen" instead.
But we're straying off topic. You were saying something about numbers being confusing? Yes, I agree they are confusing.