Nearly all people will use an appliance if it makes daily life easier. For example, almost every household has a microwave. Cooking becomes much easier if you just push a button. We also are more likely to use products that dramatically change our lives, such as the TV.
In the 20's we began to see the introduction of many of today's common household appliances: the vacuum, refrigerator, etc. For the first time Americans had money to spend on luxuries and therefore manufacturers made more luxuries available. Improvements in technology during this time , most notably the assembly line, made manufacturing more efficient and therefore cheaper. As a result the goods produced became cheaper. Household goods became a mark of success, again increasing demand and therefore production. In the decades since, technology has continued to improve production, and lower manufacturing costs and therefore product costs. In addition we have continued to try to make bigger (or sometimes smaller) and better and more types of appliances which means the last model just got cheaper. As older types get cheaper more people can afford them. If no new innovations were made, say in refrigerators the prices would never change, except to go up with demand. But because there are all sorts of new technologies to be had in the best fridges (plus the bonus of things like stainless steel and energy efficiency, things that make people want to buy) the simplest fridges drop in price making them affordable to most.
There were many factors that led to the point where almost everyone uses home appliances. In the United States, the main factor was the rise of industrialization.
In the early decades of the 20th century, the US economy became much more industrialized. this process made the production of household appliances much more efficient. When this happened, the prices of the appliances dropped and many more people were able to buy them.
In addition, industrialization led to an increase in the size of the middle class. As the size of the middle class grew, the market for household appliances grew as well. In these ways, industrialization led both to an increase in the supply of appliances and an increase in the demand for them.