Every country has its own way of doing the laundry, which is something travellers must think about when they are away for over a week. It has to be said that most hotels charge exorbitant fees to do the washing so alternatives must be found. If you are using a hotel price comparison site then chances are you do not want to spend $5 to wash a sock.
In the USA, some hotels have laundry rooms which can be used by guests. Think of the suites type hotels which come with little kitchens. Staying in the USA, despite being a rich country. people tend not to own their own washing machines. Each block of flats shares a common laundry room, which is great for the environment and is really a good idea. Do we need our own machine that gets a few hours use per week?
In Latin America washing machines are also rare in apartments. Some blocks of flats, the newer ones, have the American model of common laundry rooms. What is common in countries like Argentina is the local service wash, where you take a pile of clothes and they wash and press it for $5 or so, often the same day. Excellent news for people who pack light!
The UK used to have laundromats like in the US, self service ones, but in the UK they have largely disappeared. You need to search a bit to get to find them now, just Google the area you are in with laundromat to get local listings.