All that adds up to a carpet that needs some TLC. A quick vacuum can take care of most of the issues. Yet dirt and grime (along with germs) can make their way deep into the carpet.
What about stains? You may be quick at mopping them up, but some may have soaked into the base of your flooring. Using a steam mop can help freshen up your carpets.
Perhaps your house is located in an area where there is high humidity content in the air. Your carpet is under constant attack from the humidity and never has a chance to dry out.
You can use heaters and dehumidifiers to extract the water out of the carpet. But if the carpet hasn’t the chance to properly dry out quickly you may find it feels a little squelchy underfoot.