Yep... anybody to confirm, and whats the reason for in indoor matches.
Players have to be exposed to the same conditions. When you think about the court, there are minor differences between one side and the other and those can make a great difference. Think about the crowd. It's a very important element, if players didn't change sides, that could favor or disfavor a player, if the people behind the player were supporting him or trying to disturb him. But it's not just about the crowd. Even the line judges, some are better than others, if players didn't change sides, the shots from one of them could consecutive be called in or out wrongly.
But there are many other factors such as uneven lighting or surface damange (like bjurra mentioned) that might seem minor but put together do have a great influence in the match and how it plays out.