WHY DO POWER SOCKETS IN HOTEL BATHROOMS SAY "SHAVERS ONLY"?
It's a safety measure, and although different countries have different regulations governing the safe use of electrical systems, this stipulation is fairly universal in hotel rooms. Suppose you plugged in a high wattage appliance such as a hair dryer. If the floor where you were standing happened to be wet and if you dropped the hair dryer, there is a possibility you might be electrocuted.
No hotel is going to tolerate even the slightest chance of this happening, and therefore the "shavers only" requirement.
These power sockets use either a fuse, which will blow and interrupt the circuit if you try and use any device that draws more than about 40 watts, or a Ground Fault Circuit Interrupter.
The GFCI has a circuit breaker and a hair-trigger circuit that detects any stray flow of electricity. If the current leaving one side of a power source differs from the current returning on the other, that indicates a dangerous condition and the GFCI breaks the circuit.
Whichever method they use, "shaver only" sockets severely restrict the amount of power available. You could probably power up your phone but even most laptop chargers draw more power than that available from these sockets.
As an aside, most modern hair dryers are equipped with a GFCI that reduces the risk of electrocution but even so your hotel wants to keep you safe and sound.