[viraptor]

Another way both can be true is that many/most companies just post an ad because they need to to get started, but don't actually optimise how it works. You can easily confirm this by looking at some discussion boards about google ads, where people often ask how to fix a very bad / accidental ad placement decisions which burned through their whole budget.

On the other hand, there are companies with teams dedicated to make their ads as effective as possible and track/raise the ROI.

There's likely lots of companies even in between those extremes which don't even break even on the ads they pay for. (or don't know if they do or not) They may pull the ads and realise nothing changed.