Waterproofing is only "necessary" if you don't want water damage. Meanwhile, in the real world, digging down on the exterior and applying the waterproofing the walls there, along with a perimeter drain system is the only truly effective waterproofing.
Do you need to waterproof walls?
Therefore, you need to waterproof the area so that water does not get into the substructure of the house and cause major structural damage. It involves setting up a waterproof barrier around the floor and walls of the bathroom, including the shower.May 1, 2018
How do you waterproof a wall from the inside?
Apply a masonry waterproofing product to the walls Seal/coat the interior of the walls with a suitable masonry waterproof product. When the paint dries, the sealant forms a watertight bond to stop water from seeping through. This is how you can waterproof your basement walls from inside.