Consider this scenario. You are an administrator entrusted with a system and you are tasked to find a way to do X. You don’t really know the background history of X technology, nor the specifics of working with it.
There are probably two places that you go to first to search for insight into doing X. The first place is within your own personal resource collection. This collection can be a series of disparate text notes, documents, PDFs, ebooks, etc of a number of topics ranging from assembly programming to cyber warfare to networking fundamentals. The search function may not work as well as it should be and, despite going through 20 results you found -some- useful information but not enough to move forwards. The next step is probably the search engine online.
The first result yields the vendor’s page. Great! It’s written by a vendor. That means that this person know what they’re talking about, right? But you see the authorship date. The entry was written more than 10 years ago. Oh well, you scroll down, read what they have to say and see if it applies to you. You realize shortly after that what they have written not only did not answer your original query but it went on numerous tangents. Code this script to do 20% of this thing that you need to get done. Click on these 3 links. 2 out of those 3 links are no longer active or the project was maintained. You exit. But don’t worry, there’s another 10 tabs left to go!
It’s not all hopeless though. You come across a resource published within the last six months - technical and in-depth. Extremely. And very interesting too. And you finally come across the portal, again by the vendor. The portal is that one resource, at least, that you know the vendor will make sure to keep updated. You know that the vendor will take care of its communications in making sure that the information conveyed is done so in a clear and concise manner. The portal page does not disappoint. Communities, while the answer quality varies for places like StackExchange, can also be useful bastions of information.
The thing here is that despite all the posts published by the community, the vendor portal page is and should still be the number one port of call.