In Hilversum you will see a lot more big SUV's than in a typical Dutch city, the area ('Gooi') is considered quite posh in the Netherlands.

Yes there definitely are possibilities to make more out the existing urban area's. But wherever someone has an idea for building more houses, there always are others that are against it. In your case, building 4-5 story buildings would be seen by some as disturbing the skyline of the city. They'd rather keep their current small city atmosphere.