Underground aquifers are definitely used as the tap water source in some areas.
The main difference between spring water and tap, is likely that your tap has fluoride and chlorine to A) help with dental health and B) keep the water safe if there’s some kind of contamination on its way to your home.
If you own your home or can install one… I highly recommend just installing a reverse osmosis system for your drinking water. It needs annual service, but it’s a heck of a lot easier and cheaper than buying all your drinking water in bottles.