leaking windshield

If there isn't any sealant there the leak is there. Beats me how some folks do things. Very flat surfaces ( engine parts for example ) have a gasket between and some sort of sealant is applied there 99% of the time. Yet where a less than perfect body / glass bed and a glass with its slight variations are put together with a rubber "gasket" ( more correctly defined as filler and isolator ) sealant was deemed unnecessary ?
You can be sure that when the mfgrs laid the glass in sealant on top of the body/ glass bed, thus deleting the rubber filler, tolerances in those mating surfaces were drastically tightened and controlled.