We have many clients from various industries who use this - Ranging from virtual production, cinematics, game devs, to advertisement and automotive 
If you want dense, quickly-populating Cover of the landscape, there’s currently no alternative to Landscape grass types.
Besides, only Landscape grass supports shader-based scattering, which allows for a lot of customisation unlike PFS/FTs.
FTs also take up a lot of memory, if you use them at scale - as opposed to Landscape Grass.
It allows for quicker iteration and is literally impossible to create a detailed large world without it for practical and performance reasons.