I don't think eligibility for the green card lottery means the country doesn't use its quota. It means that over the past five years, the total number of immigrants from that country has been less than 50,000. The quota for a particular country could be small in proportion to their population, or there may not have been any quota at all in previous years. The idea is to balance some of our laws that favor bringing in immigrants from the countries where we have the most immigrants, because of family sponsorship.