I haven’t completely investigated this, but I had a basic file (a large shelf) and it was 1.7 MB. I thought it shouldn’t be that big as it is quite basic (no materials, scenes, etc.), so I copied it to a new file and now it’s just over 200KB in size. Is it that the purge function doesn’t work very well? Perhaps I’m missing something?
There are only 2 layers, all visible when purging. Zooming to extents shows no other entities.