And then you hit level 50, do one day of dailies, and can buy a Mod that completely screws over any use you claim these crafted mods have.
The problem isn't what they can ~do~, it is the availability of all the alternatives that are just as good, if not better. Modifiable weapons and armor completely removes crafters from the picture ~except for that one recipe that people might feel the need to spend money on that they really don't have to spend money on~.
Crafted gear isn't required to do Hardmode Flashpoints, which is an issue when logically the progression path is Crafted > Flashpoints > Operations. If you do dailies, if you have modifiable items, you can just ignore the gear based professions and be on equal, if not better, footing than those who took it.
Armstech was useful while leveling. Yes. This is true. I had an epic barrel ready for me every 6 levels (About the time when a green barrel is 'just as good'). Woo, yay, Armstech is awesome.
And then you hit the point where you'll spend a majority of your time on that character; Level 50. Suddenly, that prospect of being able to epic barrel all your guns isn't the brightest star in the galaxy.
I can't speak for Artificing, Synthweaving, or Armormech personally, but I do know that I'm having trouble finding a reason to keep Armstech. There's very little incentive. If I didn't gather the materials myself personally and hunt for deals on the GTN, I'd be nowhere close to breaking even on all the materials and time invested into it.