Zones were introduced to Hattrick to ease the search on the transfer list and reduce daytrading. As more and more countries joined Hattrick, buying a player would mean that you had to search through more and more countries on the transfer list. Given the HTs' choice to make Hattrick a game that everybody can play, even when having only a few minutes left per week, the zones were an easy way to reduce the time one had to search on the transfer list. Moreover some people with more time used the old system to practise daytrading.
Zones by number of users
The zone with the fewest number is leading the list.