All they do is complicate things. In today's society where communication is easier across long distances, we should have a set Earth time. In each respective area, people will learn what time the sun rises and what time it sets. Communication and correlation over long distances would be simpler, and keeping track of world events would also be easier. Agree or no?
Here's the deal. If we didn't have timezones the world would be a strange place. If we did have an international timezone, what countries time zone would we adopt? Also, people would be sleeping at like 11:00pm in one country, where it is dark and easy to sleep. Where as on the other side of the world, someone else is up and about at day time. So it wouldn't solve anything. An Australian could ask someone to play online at 11:00pm. To him that may be fairly early, but to his American friend fairly late. And if someone was talking about what time it was, and how early it may be, someone who it may be late at night for will get confused. And other countries have already adapted to the normal timezones, so it would actually complicate things further.