The circular shape is designed to encourage consensus among political parties rather than confrontation, such as the Westminster system where the government and opposition parties face each other on opposing sets of benches. The design is used in most European countries (and hence was adopted by the European Parliament). The United Kingdom of course does not, as the originator of the Westminster system, however its sub-national assembly, the Scottish Parliament, uses a hemicycle.
Some Westminster system countries outside the UK, such as India and Australia, have confrontational benches but the end segment is curved to create a partial hemicycle, while other countries, such as the People's Republic of China, have one set of benches facing towards a stage area (though this reflects the one party system in operation there).
In the case of Australia, the two largest parties are still facing each other, whereas in an the Scottish Parliament's hemicycle the largest party sits in the middle. However some hemicycles follow a strict left right arrangement with, for example, a left wing governing party sitting on the left and the right wing opposition on the right. In these cases election results are often portrayed in the hemicycle to show the results of left wing or right wing coalitions (reaching 50% in the centre where centrist third parties are located) for forming a majority.