PIE allative?

If you can reshape PIE phonetics from considerations of symmetry
(glottalic theory) I suppose you could do the same with cases...

How come, if PIE had an ablative (from-case), that it didn't have an
allative (to-case)? From the little Latin I know I gather that the
accusative can sometimes function as an allative (Romam). Why not
split up the accusative into accusative and allative, to preserve
symmetry?

Finnish has a to-case (allative?) in -n. With a separate allative in
PIE this would mesh nicely, or?

Torsten