I believe this is known as "extra floral nectar" & is certainly useful in attracting pollinators. Though this nectar is also produced by leaves in some species. Regarding pollinators, certainly mothe seem to be the obvious choice, though as to which ones thats a trick question. Since the natural habitat of Sansevieria ranges from South Africa right up to North East Africa & Arabia (&India) then there must also be a wide range of moth species. Some Sansevierias have a flower which only opens at soil level & it is belived that ants or even small rodents can pollinate.

Well, if it is ants, it wouldn't have to be so picky as to only open at the soil level. The ants around here find their way onto & into EVERYWHERE & EVERYTHING where there is any sticky stuff. Ha. They even carry their cows (aphids & mealy bugs) along with them to high up new leaves to REALLY make me mad.
That floral nectar is also on hoya flowers and I imagine others.
Marcy