Comment by VorpalWay

I think they are making the bet that most modules won't be imported. For example if I install scipy, numpy, Pillow or such: what are the chances that I use a subset of the modules vs literally all of them?

I would bet on a subset for pretty much any non-trivial package (i.e. larger than one or two user facing modules). And for those trivial packages? Well they are usually small, so the cost is small as well. I'm sure there are exceptions: maybe a single gargantuan module thst consists of autogenerated FFI bindings for some C library or such, but that is likely the minority.