Most countries have a neutral conductor that is at or near earth potential. In most rooms, you would survive a mains shock because human skin resistance is high, and people are usually dry, wearing clothes and shoes of insulating material, and standing on a carpet or a floor made of insulating material. All this adds up to a very high resistance, so the current flowing through you is tiny.
In a bathroom, there are metal taps which are earthed, and if you are in the bath, the water all over your body reduces your resistance greatly, so a mains shock is much more likely to be fatal. Or you might be standing on a wet floor in your bare feet, with similar results.
In the UK you are allowed to have a special shaver unit, where there is a transformer which is centre-tapped to earth, reducing the possible shock to half the mains voltage. A mains electric razor or other appliance will be double-insulated so you can't come in contact with a live wire. A regular 3-point socket is not allowed in a bathroom.