First of all, thank you for a large series of well written and constructive responses. It continues to reinforce why I love EnWorld
You guys have sold me on Plant Growth, thank you. However, I'm still not convinced on Fabricate.
This is like asking "Why don't bars just hire NFL linebackers as bouncers?"
This quote was cool and stuck out at me. The answer in this case would be: "If an NFL linebacker could do the bouncing of 600 bouncers, would you hire him?" That answer is almost certainly yes. (for real life reference based on the googling: Bouncers make an average salary of $27,000 / year. 600 bouncers would cost 16.2 million. An average linebacker makes $7 million a year. So its an incredible savings to hire this one "ultra bouncer", the regular bouncers wouldn't survive in that economy!
So I'm seeing several common responses, so let me respond to them:
1) "There are just not that many high level casters". Is that the case in most of your campaigns...so would a 7th level PC really be the most powerful person on the planet in all of your worlds?
I agree that high level characters are "rare", but the truth is it only takes a small handful of such characters to do the economic changes that I am describing. And if high level characters are "non-existent", than you have other problems when a player gets to not even mid levels and now is more powerful than everyone else on the planet" There is nothing wrong with that campaign, but I doubt its the norm.
2) "High level wizards have more important things to be doing".
Now sure, sometimes the high level wizard (and again we are talking 7th here, not like 15th) has to save the kingdom, beat back a monster, slap down a wizard duel against his nemesis, research the next great spell, etc. And during those times it makes sense that he wouldn't be crafting.
But Wizards like gold too, and plenty of it. In fact, they are the only class whose power is directly tied to gold (as acquiring spells by default in your spellbook costs gold).
For just 1 spell and 10 minutes a day, in a few years a 7th level wizard could become rich beyond imagining. They could have magical components shipped to them from all over the world. They would have all of the ink to scribe spells they could ever want. Heck they could just pay non-wizard adventurers to go kill all of the important monsters they need for components.
Now if you operate in a world where wizards are literally adventuring 365 days a year, than more power to you. But if we assume a wizard has any downtime on their hands...and it requires so little effort to generate so much money....why wouldn't they?
3) "NPCs wouldn't do it, but if PCs would more power to them"
This is a similar notion to my thoughts on Item 2, but now its the PC that gets all of the crazy benefits. If we assume a world where gold is useful (can buy you favors, spells, maybe have some adventurers bring you some magical components), and that PCs have at least some downtime here and there....than for a 7th level wizard this seems so powerful you would have to be an idiot not to do it.
For one little old proficiency the wizard during his downtime generates more gold than entire adventures. He has more money than the rest of the party combined.
And not just money....fame. Take that armor example I mentioned before, imagine the prestige that wizard would have. The king himself would invite him to his castle to stay, and would ensure every need of his was provided for. He would become one of the most important people in the kingdom...maybe the world. The other party members....nay, not so much.
Ultimately I almost come back to... yeah, I can always find a hand wave to explain why it doesn't happen. But it always feel contrived. In certain campaigns, they are magically restricted enough that it makes sense why it wouldn't happen. But for the standard dnd magic level, and standard level ranges in the world....I just can't see why it wouldn't go that way.