It’s generally said that the dollar sign is in front to stop people adding extra numbers to written cheques. Since the end of the number is finished with .00 and the start is $ there is no room to add anything extra.

All the checks I've seen have a box for the number and the $ printed outside the box. There wouldn't be room even if there was no $.

Also that's why the amount is written in words below it, a double-entry to prevent one of the two locations from being modified.

Does Turkish say “out of ten, four” rather than “four out of ten”?