I think everyone wants good fluid dynamics/animations.
Be it water, ketchup, cum, etc. Having fluids act like the fluids they are is useful.
If you look at most animations, the fluids no matter what they are made of are ridiculous, some lack viscosity, others look like cement mixture.
Onto specifically facial cum, maybe not the largest need, but some will, on actual real world accurate fluid dynamics of both Newtonian and non Newtonian fluids, with correct coloration/flow/viscosity/dripping/adherence/etc that is definitely needed.