Carpet re-stretching is so common because many home builders and carpet retailers outsource the installation. To be competitive, they want to keep the price low for this service. So, they give installers a limited amount of time to do an install. That means they just use the knee kicker to install carpet, which speeds up the process but lacks the quality.
What you really want to install carpet is a “power stretcher”. This doesn’t actually use power, but it is a big lever that stretches the carpet from one side of the room to the other. Properly done, a carpet stretches 1-2% of its length. So, on an 18-foot room, that can be as much as 4 inches. No human can do that with a knee kicker.
When not stretched properly, the carpet will get bubbles and wrinkles over time. If you are looking for a reputable company to install your carpet properly the first time, we recommend Baldwin’s Flooring America.