I think it's just that HN audiences is generally detached from the harsh reality of the "money people" who make these purchasing choices and are generally choosing the safe low friction option, that lets the business free to focus on product development and sales that are the core of business, rather than wasting resources on building and managing IT infra from FOSS scratch for the sake of avoiding $BIG_TECH.

If your business is making and selling a new type of energy drink or gluten free bread, you're not gonna bat an eye on going all-in on Microsoft Office 365 and Azure for your IT infra so you can focus on the product.

Same story on how even software-first companies like Google just default to using SAP for ERP and be done with it instead of trying to write their own solution for no benefit even if they technically could, why bother when they can just focus on doing what they know best, getting you to click on ads, and outsource the annoying boring part of the megacorp business to SAP.