It's the other way around too. Once you can use this with PostGIS, the platform becomes immediately more useful because you can now interact with most GIS data, tools, and standards.

Think separation of concerns - use a storage engine for spatial data and a separate engine for rasterization and tile generation - and how this could be used in a market that still expects proprietary data AND software.

The spatial data already exists and an entire industry built on pretty much a couple of companies tools (ESRI, Oracle, DigitalGlobe, GeoEye). You need to have the protocols or interfaces to interact with the storage engines. It will probably be another 50+ years before those databases change in any sort of major technological way.

In many cases the tile generation and access to those tiles (usually via web interface) is often lacking or extremely difficult / expensive to setup.