Identical twins are super interesting to researchers, because when studying the human body, it's really hard to get a control group.
Even fraternal twins are interesting to sociologists if they were raised in the same household, since for the most part they would have the same or very similar lived childhood experience.
One thing I found out after my wife and I discovered we were having identical twins is that manipulation of embryos increases the odds of having identical twins.
In our case, the embryos were frozen, thawed, a few cells removed for pre-implantation genetic testing, frozen, thawed, and implanted again. Two embryos were implanted, but only one took hold. Then the one that took hold decided to become two people.
Fraternal twins are much more common than identical twins, because most IVF clinics will implant two embryos at a time, due to the chances of implantation failure.
(Also, for non-IVF, fraternal twins are also much more common, for different reasons.)
FWIW when my wife and I went through the IVF process our provider (RMA, who are basically a large US-wide franchise) informed us that multiple embryo transfer was not an option offered by their clinic (not that we would have chosen it, but point is it wasn’t presented as a choice).
Even fraternal twins are interesting to sociologists if they were raised in the same household, since for the most part they would have the same or very similar lived childhood experience.