Or it could simply be that they are not profitable to make...
That was the case with the local manufacturer. He decided that there was simply too much labour, and too many rejects too continue making them. BTW, the head of that company is also a technical rigger, so I bet he knows more than you or I about safe loads, shock loads, blah, blah, blah... and he never had a problem making them until he decided he wasn't making $$$ from them.