Most of the time, SVGs come with a lot of cruft
This might be caused by a variety of reasons: messy/unstructured layers and groups, there might be stray raster images, or just the exporter naturally embedding its own fingerprint on it. For cases like these you might be surprised by how much you can shave off an SVG, and how much cleaner the markup can be specially if you have to work with it. Who doesn’t want something cleaner and lighter?
When using SVG assets then I suggest passing it through Jake Archibald’s SVGO online compressor a nice online tool to optimise your SVGs. You can also add it to your build setup or do it via Sketch plugins.
There’s a bunch of settings you can fiddle around with and get the best settings for what you are trying to achieve; you don’t want to “collapse useless groups” if you’ve structured the groups for purposes of animation, for example.