Facebook and Google have huge tech operations, but Facebook and Twitter are content distributors and market aggregators, not tech companies.
You can buy a jet or a rocket, but you can't buy a Twitter or a Facebook. You can't even hire part of their stack. (FB has content deals and APIs for advertisers and marketers, but not - so far as I know - direct access to the servers.)
Which is why AWS is a tech company. But Amazon is an online store that happens to use tech.
It's like saying book publishers are really just printers, or FedEx is really an airline and truck driving company.
Some publishers do indeed do their R&D for print operations and logistics. But they're still primarily content houses. Any engineering that happens is a means to a productive end, not a product in itself.
Facebook and Google are generally considered tech companies.
https://duckduckgo.com/?q=google+facebook+tech+companies&t=o...
And of course the current attempt is to not have advertising be the primary income source.