Houses need to last a very long time. The plumbing system could last 75+ years, the house could last 100+ years if you keep up with maintence. This means switching to a new technology that turns out to not work as advertised can be a disaster.

There used to be a copper water pipe replacement called polybutylene. It was cheaper and easier to install than copper, but it turned out to have a short lifespan with leaks happening early in it's life. You might not be able to get homeowners insurance if you have these pipes requiring them to be replaced. They started being installed in the 70's but it wasn't until the 90's the problem was discovered. That's 20+ years of what was thought to be a proven technology.

So construction companies, the reputable ones at least, don't want to leap into something new only to find out many years later there's some horrible problem that could not be forseen.

Then there's the "we've always done it that way" people. Even when something is proven they refuse to use it because they have always done something a different way. These are also the people that shake hands with danger because they think it's manly to breath in rock dust and get lung cancer. When you are near a construction site and hear a guitar riff that's somebody that doesn't know what they're doing. https://youtu.be/Mmrs9GYkbqg

Union labor