Here’s an answer I did not anticipate to the alleged stinky house epidemic: people don’t air-out their homes any more. Also, people have less tolerance for smell. From readers:

Jonah, the cause of the air freshener craze can be traced to the fact that suburban Americans don’t open their windows anymore. This is probably less true up north where central air isn’t as common, but here in the south it’s a rare sight to drive through an upscale neighborhood on a beautiful fall day and see all the windows open. Closed windows equals musty house.

And:

Jonah,
A big part of the problem is not true stinkiness, but
mustiness caused by the fact that few people air out their
homes anymore. The homes are airtight to increase the
efficiency of the a/c or furnace, but that means they don’t
get aired out, either.
But, yes it is the Frenchification of the home: don’t clean
out the smells (by opening the windows), cover them up with
a different stink (I can’t stand most potpourri or candles,
etc.). I wonder if any studies have been done on the
health impacts of these scent chemicals being so prevalent
in the air….
(Disclaimer: We burn candles in the kitchen occasionally to
cover the smell of pungent food or the infrequent mistake.)

And:

Jonah: How about this? The issue isn’t dirty houses. The issue is that many people aren’t familiar with real home smells. Less cooking means less cooking smells. The hermetic environment of most homes–and most everywhere we go–makes the slightest deviant smell a problem. Don’t you now people who won’t saute a fish because the kitchen will smell like a fish? And there are many people stuck in that pre-adolescent stage where everything not light and bright is “ucky”. They can’t accept that poop does stink, and so the need for immediate air freshening.

And: Speaking for the ladies:

I don’t think all the air freshener commerercials are all about masking smells in your house. I think it’s mainly a “chick” thing. Notice how many people go to candle parties, etc. We’re just into smelly things. I like to wear perfume and although I’m not a big candle person, I do have candles (hyacinth) that I burn because they smell good. I happen to find that most of the commercially-scented stuff is too overpowering for me, so I don’t use it. Just don’t expect me to use one of those evergreen scented hanging thingies for my car. FWIW