I remember asking the same thing when I was going for my II. I do not remember exactly, but I think we are all on the same track. It has something to do with TERP design specification and obstacle clearance. The exact reason why is probably specific to that airport but again, it probably has something to do with required obstacle clearance for a non precision LOC approach vs the precision ILS approach. Either on the approach end or missed approach end.
I know sometimes they will even have multiple ILSs to the same runway because a regular ILS which takes you down to 200' ABTZE would require a pretty steep climb out while the other ILS they publish may only take you down to 600' ATDZE but have a regular climb out.