A remarkable aspect of philately is that unpopularity breeds further unpopularity. It is truly unusual to see a good collection of nearly any South and Central American country. Brazil, Argentina, Mexico, and Cuba are exceptions, but for the other twenty or so countries that make up the rest of the southern Americas, collections that are even 75% complete for major Scott numbers are quite rare. The reason is financial but not in the way you might think. Take Ecuador, for instance. It is a country that is just below average in per capita income but with a large middle and upper middle class and several large cities (philatelic popularity is related to rates of urbanization). There are few real rarities by price among its stamps, and its issuing policy is conservative and appropriate. It should have a decent number of domestic collectors as well as an active expatriate collecting community, and yet I can't remember the last time I've seen a mostly complete Ecuador collection.
The same is true of most Latin American countries, and when you move away from major Scott numbers to the thousands of minor varieties that Scott lists, the number of comprehensive collections moves from small to virtually nonexistent. The reason for the lack of good collections of these areas is not lack of native collectors, though that is contributory; it is simply a lack of material. More collectors couldn't collect Uruguay or Bolivia even if they wanted to. The material simply isn't available in sufficient quantities for it to be offered enough for collectors to want it. On eBay today, there were less than a thousand Ecuadorian stamp items offered (and most of those were covers, odd ball items, or missorted lots from other areas) compared with 441,000 US stamp lots. That's 2/10 of a percent as many. There are hundreds of lesser priced varieties that are listed in Scott that I have never seen offered