For example, take a look at Albert Einstein's Google Scholar profile. He's not the top cited physicist. Not even close. It's because other researchers don't explicitly cite his papers. https://scholar.google.com/citations?user=qc6CJjYAAAAJ&hl=en...
Same with Tim Berners-Lee and the World Wide Web. Imagine if his original paper were cited every time someone deployed a web site.
If I’m in the private sector, and I rediscover something from first principles, it is not my responsibility to go search all academia to see if someone’s done it before so I can cite their work.
If I rely on a code library that doesn’t explicitly cite papers it was built on, it is also not my responsibility to go find all the papers that it might’ve been built from and cite those papers.
Spamming citations is unnecessary.
Eh, I think the correct answer is: read it, then cite it.
You're not really supposed to cite something without reading it, as it might say something different than you think. But sure, citing it w/o reading it is better than not citing it at all.