Remember that sprinkler systems are now mandated for group housing.
The high cost of retrofitting that into an older house, plus increased electricity and wiring demands, plus plumbing requirements, plus bringing everything up to code, plus current students' upgraded expectations (one bathroom per floor? no private bedroom? horrors!) sometimes mean it's more cost effective to build.
OR a total remodel would cost as much as a new build.

I believe all of the sororities are sprinkled...now the fraternities that's another story for another day!

Back many years ago when I was at Ole Miss, about half of the fraternity houses were 10 nails and a wad of chwed gum from falling down.

After the ATO fire at Ole Miss, the state imposed a sprinkler requirement on Greek housing. However, some houses were grandfathered in. Our house a MS State was one. Later, the Fraternity mandated sprinklers for all our housing (I was Director then) and the MS State house had to comply. So all our houses - with a few exceptions - are sprinkled. However, there is not a federal requirement for it and not all states, municipalities nor campuses require them.