What also has to be considered is that appealing to the SCOTUS is an EXPENSIVE proposition. Hence, a lot of cases that could be reviewed successfully are NOT.
That was my first reaction, as well. Bringing a case to this court has got to be mid-way into six figures, not figuring on whatever courts may have been traversed before. From my brief but definitely nonzero exposure to civil cases and plenty of paralegal experience assisting my brother who is an attorney; I would guesstimate that well more than half of all lawsuits simply drop dead after completely exhausting the financial wherewithal of the plaintiffs. [read that sentence again]