Maybe he just likes building things that others find useful.

When I was younger I rented furniture from a company called CORT. I happened to notice on the contract or receipt or something, that it was a Berkshire company (I didn't know that before then).

If I were Warren Buffet, I would have been happy to know that someone was a satisfied customer of one of his companies. I got some decent furniture for a few months at a reasonable price.

Just like I'm happy when someone is a satisfied user of my software.