japanese counting systems

Last night during my Japanese lesson we started looking at how the Japanese count things. It seems to be ludicrously complicated...

To count things they first divide things in to different categories. Each category will have a different counting system. We looked at the 8 most common counting categories.
1. People

2. transport and mechanical (cars, cd players, radios, bikes... that sort of thing, but not boats and trains- they have their own counting systems)

3. small animals and fish (cats, dogs, goldfish...)

4. books and magazines

5. pairs of footwear (anything worn on the feet including socks)

6. round and small things(apples, eggs, plates...)

7. long and thin things(pencils, bottles of beer, cigarettes...)

8. flat and thin things (handkerchiefs, postcards, stamps...)

It is confusing enough to work out which category the thing you will be counting goes in to(an ashtray is small and round, not flat and thin, a rabbit is not counted as a small animal but as if it was a bird.), but then each category will have a different way of counting. So to say 3 eggs or 3 dogs or 3 dogs eggs would each have a different word for 3. There are lots of other categories on top of these 8 as well. Bizarrely chairs have their own method of counting. So at some point somebody decided we need a new counting system for counting only chairs and other people agreed with them and they put a system in to place. Why didn't someone at the time they came up with all these counting systems say "how about just the 1 way of counting. That would be a bit easier wouldn't it?"