In Israel, if you are learning, you will probably be learning forever or at least for a very long time, so that is not a reason to push off marriage. Also, once you are married, you at least get a Kollel stipend.
If you are learning, it means that when you get married, it will be your wife who will be supporting you, and Bais Yaakov girls in Israel finish school(including professional training) at 20. Many of them do wait until they have finished school to get married, although if the parents are willing to support them and they want to get married earlier, there is no reason for them not to.