I actually saw an article about this
Travel Writer Scandal Rocks Well Known Publishing House
Quoting goodfish
Once the internet really took over, published guidebooks became obsolete.
LOL. Given the large selection of guidebooks at my local bookstore (was just there yesterday), they're definitely NOT obsolete. I've never used one for hotels or restaurants, and I never trust them for hours or entry fees but have used them for background info, grouping attractions by my interests, etc. They're also nice to have when cell service is sketchy or non-existent, and for browsing in the car on road trips; just did that with a Vermont guidebook a couple months ago.
I used to get AAA books (which I did use for hotels and restaurants) and Triptiks for trips in the USA. And back in the day my parents got something similar. But the AAA no longer does the triptiks the way they did - Google has superceded them. In Vermont there are areas where there isn't good cell service, but there are work-arounds.
I also used to take a guidebook out of the library and take it with me on a trip and just return it after I got back. So I wonder how sales are for those guidebooks that you saw in the store.
As for the idea that a writer would take freebies - back in the day I would read Temple Fielding's guidebooks where he addressed that issue, and explained how he did his books. So I am not shocked by the idea, although probably it should be more transparent.
I used to travel Central America with the South American Handbook (still got some copies somewhere). Or at least the sections for the countries I was visiting (having a job max. time for a trip was 1 month so limited countries).
And I'd make complete notes on errors and omissions and post them in after getting home. And invariably my notes would all appear accurately in the next year's edition.
But I guess these days online wikis have replaced printed paper with benefits. I just can't understand why so few contribute to them (I've made many thousands of edits to WikiVoyage).
Ian