Its a vector graphic spec with support for raster embeddings. Using it to hold primarily raster data feels like an underutilisation of the vector capabilities.
A PNG would have been better, but a PNG is not programmable, so I lamented the SVG spec not having a programmable bitmap, since lots of people use it for plotting data.
That seems like it would be a lot of duplication of effort. A vector format that also has its own raster codec (and having to deal with compression, different metadata, etc?). Seems like the worst of both worlds, vs just using Canvas to output programmable rasters. Different implementations/browsers already have enough trouble outputting SVG as it is, making it even more complex/powerful would be counterproductive, I think...
A PNG would have been better, but a PNG is not programmable, so I lamented the SVG spec not having a programmable bitmap, since lots of people use it for plotting data.