[Pseudoscience-is-malarkey (OP)]

In many futuristic works, there will be a sophisticated computer that can answer almost any question posited to them. For example, throughout the Star Trek shows, movies, etc, you'll see one of the characters asking for facts on a particular issue.
Picard: Computer, what is the predominant material in Dyson Spheres?
Computer: Hematite.
Picard: Thank you.

Here's the problem with that: no one ever seemes to ever ask the computer where it gets its facts. When we in the real world ask fact-finding questions to our virtual assistants (Alexa, Echo, etc,), they say where they sourced the answer.

[Halc]

Picard: Computer, what is the predominant material in Dyson Spheres?
Computer: Hematite.
Picard: Thank you.

Here's the problem with that: no one ever seemes to ever ask the computer where it gets its facts.

I love how they still name it 'computer' instead of giving it a cute name like Alexa or something. But they don't for the same reason no naming of source of data is involved: It's a fictional show and naming the computer something cute would leave some viewers unaware that it is a futuristic machine being queried, and the data source is not listed since doing so would not add to the plot. Writing for a TV show is very different than an attempt to simulate real discourse on a ship with all the same technology.

BTW, we already have a computer that can answer most questions. OK, it's ability to parse out the actual question being asked is still quite crude, but the answers are most often there.

[alancalverd]

naming the computer something cute would leave some viewers unaware that it is a futuristic machine being queried

Hal's self-preservation was central to the plot of "2001", and "Blake's Seven" had two computers named Zen and Slave. "Red Dwarf" featured Holly - eventually played by an actor named Holly.

Given the universality of the internet and the English language (all Hollywood aliens speak English) it is reasonable to assume that  all scifi computers can access Google and Wikipedia, and every sentient being has uploaded all its data to the Cloud.

[Bored chemist]

"Blake's Seven" had two computers named Zen and Slave

You missed one.
https://blakes7.fandom.com/wiki/Orac

[Origin]

Here's the problem with that: no one ever seemes to ever ask the computer where it gets its facts. When we in the real world ask fact-finding questions to our virtual assistants (Alexa, Echo, etc,), they say where they sourced the answer.

The reason is that it is entertainment and not the real world. 

[evan_au]

Asimov's Foundation series had Encyclopedia Galactica.
https://en.wikipedia.org/wiki/Encyclopedia_Galactica

The Hitch-hiker's Guide to the Galaxy was mentioned frequently in the book of the same name. It was less exhaustive - the entry for Earth was "Mostly harmless".
https://en.wikipedia.org/wiki/The_Hitchhiker%27s_Guide_to_the_Galaxy

But even in Star Trek, there was often some character who could conveniently pull up obscure facts in their field of expertise - very useful if your audience is 300 years behind the times (this was not limited to Mr Spock and Data). If all else fails, ask the all-knowing Computer.