Our public high school stopped ranking a number of years ago and I believe it was due to students running into problems when they were applying to schools that used rank as an important criteria. I just looked that the deciles and it looks like nothing has changed. The 75% spot is a 4.1 on a 4.0 scale and 50% is 3.6.
I would imagine students could have run into trouble, being ranked 350th out of a class of 500 yet maintaining a 4.0. This would only get worse for the mostly A student (with a few Bs) ending up ranked in the lower half of the class. Not the message one of the top schools in the state would be looking to send on applications.