Currently, we only only have SDL 1.2 support.
SDL 1.2 apparently does most rendering in software. This is fine for most of our use cases, except smooth resizing. Smooth resizing a large image in software is not fast enough for e.g. a fluid zoom animation. Smooth resizing is also useful at zoom levels <1 - nearest-neighbor-downscaled images are quite ugly, and realtime software downscaling, even at powers of two, is not feasable on older hardware at high resolutions. Other perks that 3D acceleration provides is rotation - equally slow in software, but fast in hardware.
All of these are not available when using only SDL.