Carpet cleaners compete with one another on a variety of scales for new clients. The facets of the carpet cleaning industry vary depending on the city you are in, and what the general carpet cleaning needs of its residents are. For example, in Denver, carpet cleaning companies know they have to remove snow and salt stains from carpets after the winter. In Arizona, their equipment needs to be able to handle sand! Common sense can help you find more examples, I am sure.
Personally, I do not need to hire a carpet cleaning company on a regular basis, simply because I have hardwood floors in my house. That was deliberate, I am not a big fan of the chore of carpet cleaning.
However, I grew up in carpeted homes, and cleaning carpets was an intricate part of the chores of my childhood. I recall many spring cleaning trips to the grocery store to buy cleaning supplies and rent a carpet steamer for the worst steams that my childhood had visited on my parents flooring.
I am not a fan of spring cleaning when it is in a house with 5 people. When I live by myself, I certainly am okay with cleaning, because the mess is not anything worth talking about. One person, especially one who is generally neat (like myself) rarely finds himself needing to do extensive cleaning. Performing regular chores makes things much easier.
I can not say what anyone else should do when it comes to their carpet cleaning, but if it is my living space you are talking about, I could go without carpets. I like a nice rug, though.