For stranded and flexible conductors going into a screw terminal, yes, and it's worth insisting on.
A bare stranded end under a screw gets crushed unevenly. Some strands take the clamping force, others splay out sideways and carry nothing. The effective contact area shrinks, resistance rises at that point, and the joint warms up under load. Warm joints loosen, and loose joints get warmer. That cycle is behind a good share of the terminals that end up discoloured inside distribution boards.
A ferrule gathers every strand into a solid cylinder that the screw can clamp properly, and it stops stray strands wandering across to the next terminal. Use the right size for the conductor, crimp with a proper ferrule tool rather than pliers, and don't tin the end with solder instead, because solder creeps under pressure and the joint slackens over time.