CapnZapp
Legend
This.Even the official adventures and dungeon adventures tend to change the powers and such to suit the needs of the particular monster/npc.
Let's take the example town (Fallcrest) from the DMG as an example.
While Wizards of the Coast can add standard monsters (straight out of the MM) and include their stat blocks, you would not want to do that anyway.
Creating new NPCs (and unique monsters) is much cooler anyway.
In 3E, everybody would care if "Barstomun Strongbeard" was a properly built level 4 NPC Dwarf.
Not so in 4E. Who cares whether his "Dodge and Throw" or "Stand Your Ground" powers and properties are available to NPC Dwarfs (in the MM) or for that matter PC Dwarfs (from the PHB)? (I think one is a standard ability, the other a unique one - but again, this matters little)
If all we're trying to accomplish is a level 4 Fighter Dwarf PC I can do that myself (or rather, I can look it up in Strack's excellent Book of NPCs!).
In fact, if you are a publisher wanting my money for your adventure, I would expect you to create new cool NPCs.
Especially Elite or Solo NPCs - there are too few of those as it is. (If I want a level 11 Solo Necromancer, yes there happens to be one in Dungeon Delve, but that is probably the only one to choose from)
So really I think this so-called restriction is a blessing in disguise for us players. And not really a restriction for designers. (Yes, it's more work creating your own goblin types, but it isn't really a deal-breaker)
We all agree referencing monsters with just a page number is a pain - so this forces 3PP designers to come up with new and unique NPCs and monster variations.
Yes, this protects the Monster Manuals (which will remain the only common ground), but most importantly, we players can expect more unique NPCs with unique powers in adventures!