But it still tends to have large blind spots where the source is (a) pre-digital or (b) of interest to a relatively small total number of people.
Try heading to your local library or a used book store (Goodwill works in the US), find a technical or history book older than ~1980, then attempt to find the content in Wikipedia. Especially in history, the hit rate isn't good.
My private bookmarks won't get deleted by a zealous reviewer five minutes later.
It can be hard to contribute to Wikipedia without enmeshing yourself in the politics of it to protect your contributions from deletionists. This gets covered every few months on HN.
In the late 19th century there was a strong drive in academic history towards the idea of "total history": comprehensive accounts of everything that mattered from the beginning of recorded history to the current day. All these incredibly well educated German historians started outputting 20 volume world histories.
And no-one except a historiographical specialist would read them now.
They drank an ocean and pissed a cup.
These days most books have a copy online.