Your carpet is going to get dirty at some point, and there isn’t much you can do to avoid it short of stripping it all and replacing it with wood floors. It could be anything that makes it turn out that way, from wine and food stains, to muddy feet and the general passing of time.
Either way, there will come a time when you have to ask yourself if you want to hire a professional carpet cleaner or go and do it yourself.
Whichever method you choose has benefits and disadvantages, so it’s important to do your research before you make any choices.
An example would be that while DIY carpet cleaning is often miles cheaper, it also requires a lot more time, effort, and hard work to get the job done. Professional carpet cleaners are more expensive, but they have more knowledge and training, better equipment, are faster, and also have insurance in case your carpets are damaged while being cleaned.