Seems like one of those patterns with limited demand. Other than the baseline demand from collectors, it's probably a bit too large for a practical carry knife and for those times when you need a longer blade, the blade profile of the Toothpick may not be as useful as some of the bigger hunter-style blades. I don't think blade length regulations are a major factor but they may play into the demand somewhat. Also, at least historically, whether justified or not, the Toothpick pattern is viewed as being on the more weapon-oriented end of the knife spectrum (when not used for fishing), and that segment of the knife consuming market has other modern options.
Collectors who just like the pattern itself for display seem to be attracted to the much smaller Tiny Toothpicks for display, since those are one of Case's most popular patterns and offered in almost every one of their handle options.
So with all of those counter-trends, I can see why there aren't really that many of them out there, at least in modern production.
Heck even the GEC toothpicks, which are truly excellent knives, are slow movers according to several of the GEC distributors who post here.