You must be referring to the Blue Dot of old.    The ones being made during the 80's-90's which would punch up 85-88 on the durometer.   *SIGH*  (I would actually like one of those too!)

Anyway, the reasons are there is virtually no demand for it and secondly they found it difficult to make anything with such a hard shell nowadays. 

With that being said, even the White Dots being made today are nothing like the ones being made in previous decades.   Today's dots are much softer and therefore have much more hooking potential.

I know, I've complained about it. 

The duro readings make a huge diifference for me.   Very noticeable due to me being extremely rev dominant.   (450-500 rpms but only 12-13 mph ball speed)