Is it just so they can say "not my fault, our project is only using big name frameworks, DBs, etc so I did all I could?"
Or is it because they don't even begin to understand what's going on in the tech scene and just buy what appears to be the most shiny, expensive solutions?
Text files would have been enough to cache the data. But you never know how a project can change over time so I proposed PostgreSQL or IBM DB/2. The latter in case they absolutely wanted to pay for a database and they are already using an IBM AS/400. (We were using PostgreSQL and Informix.)
At the meeting they said they have already bought a license for an Oracle DB. Without consulting us. So we were forced to use it without prior experience.
Expensive parties, gifts etc
A vendor once sent me a mug. I had to open the box in front of a witness.
It is. It happens all the time. I get similar offers regularly in my growing startup. It's usually couched better than that, but it's not rare.