For many companies, the home page is probably simply not used for selling their product or informing new people about the company, and instead serves more as a symbol of the company's aesthetic and a way to welcome and comfort visitors.

Think of it more like the well-appointed lobby of an office headquarters. I don't think anyone would expect the lobby of an office building to explain what the company does. It's just supposed to look nice and welcoming.

This makes sense to me. You generally don't see uninformative homepages from consumer software-as-a-service or direct-to-consumer companies, for instance. Airbnb and Airtable both seem to immediately explain in fairly clear terms what they do, for example.

Even massive software companies with a huge range of products that self-serve to business customers have pretty explanatory homepages. Salesforce is a decent example.

I think the home pages that get these sorts of complaints are either companies that don't have product-market fit (and thus don't even know what they are yet), or companies that have long involved sales processes with large enterprise clients where they probably tend to negotiate highly-customized services. An example of the latter that comes to mind is Splunk, whose website uses a lot of buzz words and seems to basically be saying "trust us, if you're a big company with a lot of data, we can do anything you need regarding your data."