the volume in a pipe is a lot less than what you'd find in a tank, especially considering the pressure in said pipes is usually one tenth of a psi (.6 kPa)
In the US it's typically more like 0.25psi, I don't know about elsewhere.
But it's connected to what you might consider a tank of nearly infinite volume. It's flow rate limited, but it's fast enough to get an entire house to explosion concentration in much less than a day. Perhaps only an hour.
Point is that we humans manage to figure out how to harness things that might be dangerous when they're useful. And hydrocarbon refrigerants can be very useful so we might figure out how to deal with the relatively small danger they pose.
I don't disagree to be clear, I'm just saying treating it differently than a gas pipe isn't totally crazy. A punctured refrigerant line will empty in a few minutes, and it's next to a compressor that'll likely generate a spark when it kicks on. Even if it just means we need to use thicker line, lets do it.
A fuel-air explosion will not be contained by a reasonable amount of concrete or masonry. The real safety lesson is to control sources of ignition and prevent the buildup of released gases.
American homes have plenty of propane/natgas appliances anyway, so what difference does one more make?