I don't know what audio formats use, maybe some of them do treat volume logarithmically, although I think this only makes sense after transforming to the freque

I don't know what audio formats use, maybe some of them do treat volume logarithmically, although I think this only makes sense after transforming to the frequency domain, otherwise your time signal goes through 0 all the time, which is not ideal when using logarithms. For the raw sample data it's also kind of inevitable to use a linear scale when you want different sounds to add nicely, if you use a logarithmic scale then adding two sounds would distort them, which isn't ideal. When using a linear scale you can hide the quantization noise pretty easily with dither which just sounds like you're adding white noise.