Ceiling

So maybe this can be a little bit of an idiotic query, however then once more i’m nonetheless an structure scholar so possibly for that, the reply has evaded me; can anybody inform me why the shops’ ceiling doesn’t connect with the mall’s uncovered ceiling system? I noticed this on the mall a couple of days in the past (I reside in Egypt, if that makes a distinction). Wouldn’t it price much less to have the entire mall run on one MEP/HVAC system?