Finishing undergrad is a HUGE blessing for kids. They don't start their adult lives with the burden of a giant student loan payment that prevents them from buying a house, etc.

Plus, going to BYU allows them to forge friendships with a bunch of really sharp LDS kids and get some really in depth, academically rigorous religious instruction (no I don't think most institutes of religion grade rigorously).

On top of that, I've been to a professional school plus graduated from an Ivy League school for grad school, and in my experience BYU is well regarded by admissions committees at a lot of excellent schools. BYU has VERY high rates of getting its undergrads accepted into professional schools and PhD/master's degree programs. There is published research that supports this.

Finally, there's the dating and marriage thing. If you want your child to date and marry a sharp Mormon young man or young woman, then BYU increases the odds of them meeting someone like that exponentially.

BYU may not be right for every Mormon kid, but I will definitely be encouraging my children to give it a very close look.