It is a very reliable method of birth control.
You don’t have to think about it every day, like with oral contraceptives. All you have to do is check for the strings every month.
As soon as the IUD is inserted you are protected against unwanted pregnancy.
As soon as it is taken out you can become pregnant.
It does not interfere with sex.
Once inserted it can stay in place for 5 years.
Nobody has to know, so it’s a good method if your parents are against contraceptives (assuming that this will make you abstain from sex).