It's not just aesthetics but is to protect the corset
A corset is not a garment that can be easily washed (or at least runs the risk of metals staining if not thoroughly dried) so yep, anything to keep the corset off your skin (body oils and skin cells and even skin care products will eventually affect the lining.)
I have a great article somewhere about what a woman could buy for migrating to the colonies (meaning New Zealand and Australia). The basic kit including something like 30 chemises and a dozen or so night shirts. This is because that is the layer that gets washed, you could boil your linens but it took a full day of stoking a fire and getting water hot enough. So you'd want to have enough shirts/chemises to get you from one laundry day to the next.
Same principle as for now, except we can (mostly) do laundry at will so a simple singlet or fancy blouse or shirt will work
This thread seems to get repeat viewings so I figured I'd just add to the mix for future answer seekers.