Why do some countries place limits on the number of terms that a president can serve while other do no?

It depends on what type of government the country is. Take an example, Great Britain (England, Britain, whatever it is called.) is a monarchy, which means that they have royal families... like how we have the president. (in the U.S at least) It can also be dependent on what the country decides to do, or the president decides. I hope this helps!