Well even when Zones in Open Source existed almost nobody used them. That said they were only available in few places and Solaris Open Source never fully took off.
I think the reason is that they thought of them as an operational tool. Its basically a cheap VM. However, led to crazy docker adoption was its use as a dev-tool and in development making it really easy to run simply stuff.
Only then people started thinking about using this seriously deploy application on mass scale with docker. And then they realized that containers on Linux were just patchwork and the security story was a mess.
Zones were developed to serve as VM replacements, so for them security and resource management was very important.
