[morganherlocker]

Along with dynamic rendering mentioned in other comments, vector data is sparse, so bandwidth is basically zero past a certain (surprisingly low) zoom. Raster tiles are a dense data structure, so you need to bake tiles to the maximum allowed zoom and clients need to download them. High zoom tiles also have higher entropy so you end up with a huge volume of images with low cache hit rates. It’s expensive for the provider and slow for bandwidth constrained mobile users.