I don't feel that there is an advantage nowadays with the availability of the app delivery systems we have now and the App tools available.
But there are times when you might need to use it. For example, a CD installation might not allow you to install without the CD unless you do the admin install or if you want to hack the MSI. Also, you may need to re-organize the file structure than what is on the CD.
In some cases, the admin install will save the custom installation options but nowadays transforms are the way to go since you are not customizing an MSI and keeping the original MSI intact especially if you want Vendor Support.