IN the days when people used boustrophedon there were not separate glyphs for numbers and even positional number orientation wasn't especially common.

As it happens the big-endian notation of hindu (aka "arabic" in English) numbers is kind of a botch in L-R languages since you have to parse the entire goddamned thing to learn anything about it (and when it's long you have to parse it r-l anyway y divided sections). At least in R-L writing you can get evenness immediately.