Back in the olden days (as our 7 year likes to say), most households had a canister-style vacuum which relied on powerhead motors and beater bars to clean up dirt from the carpet. These vacuums worked by lifting the carpet lightly, while separating it from the underlying pad. While the carpet was lifted up, the beater bar agitated it to loosen embedded dirt and in turn the rotating brushes and suction removed. These vacuums were very effective at removing dirt, but they were hard on the carpet as well, so there was a bit of truth that vacuuming too much was bad for your carpets.
Thankfully vacuum designs have changed as uprights have taken over the consumer market. SInce these do not use a beater bar, but rather rely on rotating brushes and strong suction to remove dirt, debris, and pet hair from carpeting; they’re not lifting the carpet from the padding nearly as much, nor agitating it as harshly as they once did, this myth is no longer accurate.
Fact: Dirt and dust are abrasive and if left to accumulate in your carpet they will wear down the padding and destroy the glue that is used hold carpet fibers in place. Dirt also at times becomes chemically bonded to your carpet, which will result in a permanent stain. Carpets need to be vacuumed at least once a week to avoid this long-term damage. Set your vacuum to the appropriate height for the carpet, and your carpet will last longer.