Shemeska
Adventurer
It's weird. Every time I mention this subject, someone feels the need to remind everyone it's available for free online. In fact, even if I say in a message it's available online, I've had people quote me, cut that part, and then repeat that it's available online! You didn't just do that...but you did state it just a few messages after it had already been said three times in the same thread.
We all get it - it's available for free online. If you have no issues at all with finding twelve outside sources online and printing it, or using an electronic device at your game table, cool. But for those who do have an issue with this inter-constructiveness in the APs, it remains a growing problem and Paizo appears to consider it a feature and not a bug, based on that post from Sean K. Reynolds talking about how they need to support all the cool new stuff (his words), and reprinting it in the adventure would just take up valuable space.
For me, I don't want to go hunt down TWELVE other sources of material, online or not, free or not. That's, to me, way too much stuff outside the adventure that should be right there in the friggen adventure I paid for. When I buy a hardcopy adventure intended for use at the game table, I expect it to contain everything I need to play that adventure aside from the core rules. If I have to go hunt it down online for free, I am more likely to buy from the company that supplies all that with the adventure itself.
I don't recall a single person saying "All that errata WOTC keeps putting out for 4e is awesome, because it's available for free online!" I remember a metric crapload of people complaining it was too much to keep up with, and absurd to think people could insert it in their hardcopy books, and the effect was to force everyone to the online version of the rules making their hardcopy books far less usable. I don't see this issue being that far off from the WOTC errata issue. Forcing people online to make a hardcopy book they bought usable is an issue for a fair number of people.
I don't seem to recall you once complaining when 4e heavily tied itself into their online subscription tools, but suddenly it's a huge, terribly intrusive problem if Paizo references something in an AP which if you don't own the book referenced oh no you have to look up the free online resource?
Additionally, in my experience there's an effort to try to restrict references to a smaller pool of hardcover books unless it's something that really truly makes the most sense to use and reference one of the softcover supplements.
As for the errata, that's again a different beast to offer errata for free versus providing whole swathes of content for free as open content. Errata kept randomly changing how lots of rules worked and worked in conjunction with one another for 4e, and thus people complained about a shifting rules base and printed books quickly being out of date so to speak. Changing something people paid for in print almost monthly versus providing them with free access to material that they otherwise would need to buy an extra book to use, those aren't even comparable.