During the admission in the IEP, students are expected to choose a second stream as a backup if they are unable to secure a seat for the IEP. Since the seats are limited, not every student opts for IEP.
Also, if you are financially secure then you might as well go for it without any hesitation. There is a possibility that you might not be able to secure a seat for IEP and end up with the second stream after two years which you do not likely prefer to opt for.