The fact is worms do much better in rich soils. Tropical soils (despite common belief) are very poor, because the nutrients get washed out so quickly with heavy rain (Volcanic soils excepted). For example, the soils in the amazon are red - lateritic - highly impoverished. Tropical soils rely on the very high rate of decay/quick take up - of nutrients/fast growth spurt cycle that is so typical of the tropics.
Java became a success story for 3 times per year rice harvest because of its rich volcanic soil. And is why such a small island (relatively) was able to support so many tens of millions.
Nowadays chemical fertilizers are being used instead, with some good and bad consequences (usually out at sea).
My experience with south lombok soils show me that we are beyond the boundary of volcanic - the soils are poor(very), rocky, crumbly, with a very low organic content, or a very thin layer on top. They dry out very quickly without regular irrigation/rain. Worms have a tough time in this sort of soil.
I too have yet to see a worm, but they must be there somewhere!
I am building a compost system at Sempiak Villas - a basic 3 bin/turn over system. They are big though, cos we have a large area. An enterprising colleague in Bali has (according to him) some amazing worms that work wonders in the composting process. Hope to get some soon kalau bisa!
The plan was to compost as much as we could - paper, cardboard, vacuum cleaner bags, dairy, eggs/shells etc food scraps included - but we have clever monkeys, so will have to install enclosure/roofs for that to work.
Watch this space!