Cluster are depending on pilot (NDru) or certain ships (TAdv with corrector)
Concussion, Assault, Homing, APT, Ion Torp are all too expensive; you kinda could get around that with Extra Munition, but then your ships needs to be able to load EM in the first place. That leaves out a number of fighters (A Wing, Z-95, X-Wing, E-Wing). Plus loading EM on top makes your ship even more expensive while you are hoping to get both missiles/torps off.
Proton and Plasma are fine, ok cost/value ratio. The PR because it bypasses one of the biggest problem of the missiles/torps (TL requirement, dice modification), the plasma for the extra damage. I see plasma on Redline only, PR shows on Vader and Jake.
AHM are too difficult to use (no drawback in my eyes though), and are most effective against a small number of targets (if you go for the killing aspect). Still, a nice piece of equipment, but again is only considered because it bypasses the dice modification problem + has low cost + nice extra effect (dealing critical hits).
Flechette really is too situational. If you have a build that sucks against Soontir see if you can get one or two in - problem solved.
So only newer released missiles/torps are really considered "useful", and those are trying to tackle the problems of missiles/torps: too many points spent on single use item, no dice modification, TL requirement (which makes these close to useless for low PS pilots). And even these newer releases are not good enough to regularly make it into tournament lists; while tournaments really shouldn't be the measurement for everything they show very clearly what's effective (for the points spent).
I would argue that ordnance isn't used in tournaments more due to their specialized nature than anything. If you're facing B-Wings, Plasma Torpedoes are pretty awesome. If you're facing Interceptors...not so much.
Flechette's are great against Soontir; pretty useless against a Fat Han.
There are only a couple that can be useful against all-comers (Proton Rockets and Cluster Missiles), but even then you have to use them on a ship that's designed to get good use out of them. If I knew that every list I was playing against was a swarm of some kind, I would happily spend 5 points on Assault Missiles, but tournaments don't work like that.