The biggest reason IMO is lack of expertise - the average startup engineers will be less likely to have Oracle experience and skillset. Another reason is that

The biggest reason IMO is lack of expertise - the average startup engineers will be less likely to have Oracle experience and skillset. Another reason is that there just doesn't seem to be a reason for the average startup to use Oracle HW. Oracle doesn't seem as 'agile' for startups. It's far cheaper and quicker to iterate using commodity cloud solutions. If you're an established business with a common problem domain that can be solved with an off the shelf commercial application backed by Oracle hw, go Oracle. This however doesn't fit the use case of most startups. Plus, if I was an investor and someone told me they needed $X funding for Oracle HW instead of a scalable cloud-based solution, they'd really really have to prove it. I'd probably tell them they're overengineering except for very specific industries and use-cases.