Like seriously, why can't be used the numerical form instead of the word form?

Like I was reading a book yesterday night and the author wrote "nine thousand and two hundred". WTF? Why can you just write 9,200 instead of writing it out? Plus it confused the hell out of me for I thought he wrote 9,020 instead of 9,200.

Yeah it's understandable for spelling out numbers from 0-20 (which is the general guidelines) and numbers like 1,000,000 or 10,000,000, but really? 9,200? Even numbers like 600,000 shouldn't be written as "six hundred thousand". It should be left in numerical form. Only times I see numbers written in their numerical form are numbers like 4,376.

The worst are numbers like 750,000 where sometimes idiots spell it out and makes it harder to read.

And some people prefer to write "seventy-five" instead of 75. It's not like it makes you look badass or anything, but more like irritating.

The only case where this rule works in the opposite favor is when writing "1 trillion" instead of 1,000,000,000,000 with all those stupid zeros (and even worse sometimes they drop the commas).

The English language is full of retarded rules like these.

Discuss.