Usually the bathroom plugs say for electric razors only to minimize the amperage draw on the circuit. I am by no means a cruise ship design expert, but I do understand electrical demands. The Amperage something draws is the wattage/volts. So if you have a 1500W hair dryer at 110V supply you are drawing 13.6 Amps. An electric razor does not draw very much power at all, so it is likely in series with other outlets in the area. If you are running a hairdryer and you neighbor is and you daugther is in the cabin vanity you may blow the circuit breaker.
If you note, on most ships they use 220V power sockets in the hall of vacuuming and steam cleaning. This is because 220V is twice 110V and therefore the amperage draw of the circuit is halved. Take a look at the circuit breaker in you basement, most of the breakers for lights and power sockets are 15 or 20 amp circuits. You plug too many toasters/hair dryers/space heaters in the same circuit and you will pop the breaker. This same principle applies on a ship.
Also bare in mind that a ship has limited (although extensive) electrical generating capabilities. If more power is being drawn for room usage then they need to conserve somewhere else. Like A/C or heating capabilites.
Several postings on this site and on other cruise-tip sites recommend packing an extension cord/power strip, so I bought a 5 ft cord with 4 outlets on the end. I sure hope it's acceptable. I certainly would't want to be the cause a blackout.