I think Google Search is an interesting outlier case here and Search comes from before the SaaS boom when tech companies were more compute heavy (because of colos.) Meta and LinkedIn also have huge datasets (their social graphs) but extra costs associated with storing and indexing those tend to scale with users on the platform. The growth story of the 2016+ SaaS boom was largely in these companies where compute costs scale with revenue.

Google is also a lot more than just search. Services like Gmail or Gdocs scale much more similarly to other SaaS.