Stains on Wall Next to Powder Room Sink

Look closely and you’ll see streaks running down the wall, obviously from liquids that have been splashed out of the sink or while someone reached for the faucet handles. This is a semi-gloss paint, so you’d think it would be more resistant to staining.
Two things concern me. First that whatever substance this is, may come back back to haunt us by bleeding through the new wallpaper. Oil, which can be found in soap, cleaning supplies, and fragrances, for instance, is one culprit.
Second is that, if the walls got this much splatter before the paper goes up, sure hope that the household will take more care once the wallpaper has been installed.