Some people don't tolerate well some of the ingredients in cheese. Made from milk, the lactose can affect some negatively even though the amounts in cheese are much lower than in the base product. The whey - the liquid part that forms when milk curdles - contains most of it and is separated off during the cheesemaking process.
Others simply don't care for the taste or are looking for a bargain. Gourmet cheeses, especially those imported from another country, can be expensive. Many are an acquired taste, just like a fine but unusual wine. Some, such as strict vegetarians, prefer to avoid any animal-based products but still enjoy the taste.
A large number are concerned about the high saturated fat content of some cheese and are looking for an alternative. Cheese can be relatively high in fats encouraging the development of bad cholesterol and contains substantial amounts of sugar. Along with low-fat cheese, there are non-dairy products that can help fill this need.
For all those people, there are cheese substitutes