I love the internet because it's extraordinary!

As you are saying that you “love the internet” - why - “because it is extraordinary”, based on the description of usage in Académie-Française below, I can’t see any problem with using ‘car’ here.  The proposition that needs to be explained is the preceding proposition, which is the case here.  Of course there could be some exception here I am unaware of.

This is not to say that ‘car’ would be the first choice of native speakers. I have seen it stated that car is more used in writing, but haven’t tried to verify this further.

According to Larousse and a number of other sites, car cannot start a sentence. Larousse also indicates that car always follows a virgule, but even examples on the Académie  site do not all adhere to this. 

(Car) “Sert à introduire l’explication de ce qui vient d’être énoncé.”

“Car et en effet, conjonction et locution de coordination, servent l’une et l’autre à introduire une proposition expliquant la proposition précédente : Il n’est pas venu car il pleuvait.”

Hi Hillary,

To use "car" (because) there needs to be a specific  "justification" from previously in the sentence. "Car" is a conjunction of coordination.

Example: My son did not go to school today because he has a heavy cold.

This "reason qualification" is not required in this respect with parce que.

http://www.connectigramme.com/connecteurs.html/odyframe.htm   --> cause

Have a look at this link for further explanation.

https://www.cnrtl.fr/definition/car

Hope this helps.

Jim

Thank you very much for the detailed explanation, Jim and Maarten !!

Think of car as the English "for". You can't use either to start a sentence, for example. And both refer to a previously mentioned reason that needs to be present.

https://forum.wordreference.com/threads/car-parce-que.6343/

Please have a look at Gil's comment by scrolling down this link's page.

This is a native speaker's comment which explains exactly the difference grammatically between the two conjunctions.

Jim

There are many French speakers who disagree with Gil.

Basically for our purposes of trying to learn how to communicate reasonably well in French

1. Don’t use car to start a sentence.

2. Remember that parce que is used more than car in speech and considered “less formal” 

3. If the native French speakers themselves can’t agree, we are not going to resolve it anytime soon. 

https://www.frenchplanations.com/difference-between-parce-que-and-car/

https://www.fluentu.com/blog/french/french-conjunctions/