Because the eccentric drives each piston squarely along its bore, so loading is close to purely axial with very little side component. That favourable loading, combined with robust construction, lets the design sustain pressures well above what axial piston pumps manage, and sustain them continuously.

Those defined by force rather than by speed: presses, clamping systems, bolt tensioning, test rigs, plastic and metal forming, and high-pressure test equipment. The combination of very high pressure with modest flow is the signature, and it is what other pump types cannot deliver continuously.

Very long by hydraulic pump standards, thanks to the favourable piston loading and heavy construction, and many designs allow individual piston elements to be replaced rather than the whole pump. That suits installations expected to run for decades where downtime is the expensive element.

Size, weight, cost and speed. They are physically large and heavy for the flow produced, cost more per unit of displacement than any other type, and run at relatively low shaft speeds. Any duty needing substantial flow is better and far more cheaply served by an axial piston pump.

Some designs are, by varying the eccentricity or by controlling individual piston elements, though the type is more commonly supplied fixed. Where variable high-pressure flow is required, the control arrangement should be confirmed against the specific design rather than assumed from the family.

The same geometry used in reverse - a motor converts pressure to torque, a pump converts shaft torque to pressure. Both exploit the long moment arm and favourable loading, which is why the motor gives exceptional torque and the pump exceptional pressure from the identical arrangement.

High, as with any precision piston machine, though the heavier construction makes them somewhat more forgiving than a swashplate pump. Given the pressures involved and the cost of the unit, meeting the specified cleanliness target is cheap insurance rather than an optional refinement.