We've discussed this exact question many times over there years, but like many other "why/why nots" it all boils down to Darris and for whatever reason he just decided to replace the XTB with the XB2003. (And for the record, the XB2003 is Darris' greatest seller so I guess in actuality he got that one right.) However most of us fishermen agree, "modernize" the deck/topcap of the XTB and release it with options of single or dual console, and perhaps even make it a "value line" or price it more in the normal range of the average cookie cutters... Nitro, Stratos etc... But I kinda get the impression it boils down to Darris just not wanting to pursue that market. For SURE they would sell like hotcakes, get Allison quality, performance and ride and when packaged with a 150/175 and the options list kept reasonable a person would be crazy NOT to pick that over the next competitors.
Remember also the XTB was LIGHTYEARS ahead of the competition. In the late 80s a 21ft basser was basically unheard of and many felt probably un-needed. That was still back in the days of 17.5-18.5'ers with 150 still being the max on most trails. A 21ftr laidout like the XTB was maybe more than most bassers could comprehend back then.
Build it and they will come, :very happy
RA