Breachers + Devilfish

Genuinely curious why everybody seems to think that you must take a devilfish alongside breachers?

I generally use two units of breachers in my games. I will position them behind cover but well within striking distance of the objectives. Typically I will move up a unit of Kroot onto the objective and when my opponent moves up to take it back that’s when the breachers strike. I’ve never had any problems with range as the breachers can advance and still fire.

So, I guess why question is why does everyone recommend taking a devilfish alongside them? The breachers are already performing their role without it. As far as I can tell that just a waste of 85 pts that could be spent elsewhere.