This might have to be a secret kept from new, inexperienced fishkeepers, as they might think that a few plants in the tank makes it all good for adding fish right away . . . .
I agree 100%, lauraf.
Most don't start out with that much light (a 29gallon tank comes with 15watts at my LFS). You have to spend some extra $$$ to get better light and most starting out with a 10gallon tank are not going to do that.
Add to that the fact the 90% of what LFS sells is not even aquatic plants, which just rot over time being submerged, its a wonder anyone gets started at all with plants. Decaying plant matter is just like fish poo in the water.
I was at a big-chain pets store last weekend to get my ancient cat's food (she's going to be 20 in April) and walked through the fish department. They three aquariums with plants for sale: one was bamboo (not aquatic), one was mondo grass (not aquatic) and the last had some dead/decaying anubias and java ferns (yea! FINALLY aquatic!), but each plant was burried in the gravel. I tried to explain to the fish department guy that he'd likely sell more plants if they a) stocked more aquatic plants and b) took care of those they had (I wasted my breath explaining what a rhizome was).
He smacked his gum a few times and said he'd go tell the manager, all while rolling his eyes.
He went back to doing water changes on the tanks with a python. The tanks he'd already done on the opposite wall all had fish gasping at the top and darting around like crazy. I found the assistant manager and brought her to the department. I told her something is wrong with all of the tanks the guy was just cleaning. She went to the water changing station, opened a new bottle of Prime and added some to each tank. Seems the guy 'always forgets' to add the dechlorinator.
And this bright young man is advising unsuspecting new fish/plant owners on how to care for their purchases.
Yikes!