Production costs are pretty high to do a tool run, and they probably don't think they would sell enough to make back the money and then some.
As well, they already offer 12pt deep metric, and deep sockets are not meant for high torque applications, so there is no need to make a 6pt since it doesn't meet a neccesity purpose either. On the SAE side of things, there is a lot of demand being that industrial applications are almost all SAE in America, combined with them needing a deep socket more often than in automotive applications.
It would be nice, yes, and I would buy them, yes, but business wise, there isn't enough demand or reason to make them.