Hi!
Sooo the title kind of explains it - with LWC support now being a major engine feature, VFX (like materials) need to be able to keep up with new massive projects 
At the moment Materials DO support Double Vector Parameters which can be set via Blueprints, which is great, BUT things quickly get messy when a large number of materials need to reference the same Double Vector.
Traditionally throwing the vector in an MPC will solve all of this but at the moment Double Vectors are not supported there, so materials that rely on an MPC to access the data break down over vast distances.
Spaghetti code is currently the only viable solution :')
If it is not too much trouble please look into adding these!