The real reason is to attract and onboard people onto the platform. Part of me always felt they should of just put a functional wrapper on their APIs, have an API that avoids the mutative fluent interface, and then just show some F# examples. Especially for people outside the .NET ecosystem it would show how terse, yet performant and feature rich the platform actually is. It would compare well to examples from other langs/ecosystems.

In the workplaces I've been in newer developers typically try then abandon the OO paradigm. They've seen they can get by without it and get decent performance, and there is a learning curve which experienced people have already paid for and typically then take for granted (patterns, DI, class structure, interfaces vs abstract classes, etc etc etc).