The reason they were used in the past is the incredible holding power of a taper yet easily removed.
Besides being solid they make the item rigid, motion less. Screws can be tight but the assembly still move under load.
Typically used for ball screw or acme screw mounting.
Another benefit is being able to realign the part and reream the assembly with minimal effort while maintaining the easy to remove and reseat pin.
Yes I am a taper pin fan.
I use them instead of roll pins if I can, obviously they many applications where they better suited than taper pins.