To be fair, traditionally there weren't a lot of events where you needed to figure out the number of farthings in a pound. I also read somewhere that loans were generally set at 5% (one shilling interest per pound loaned) because working out any other number was a pain in the neck. No idea of the date or veracity of that little nugget though.

I always thought the guinea was particularly funny, given that it doesn't really add much in the way of demarcation.