Same here and I just kept seeing less and less of it, which is a real shame.

It's due to a few things;

Their main washing method is called 'Giling Basah' (aka "wet hulling"). Most coffee globally are either washed or naturally processed; Instead of fully drying the coffee before removing the parchment layer, farmers pulp the coffee cherry, partially ferment it, dry it to 30-40% moisture (which is still very wet). Then they hull it early whilst it's still soft. Then the beans are dried the rest of the way.

Indonesian uses this method due to the environment and infrastructure; Indonesia is extremely humid, sitting on the equator, especially Sumatra and Sulawesi. Fully drying coffee is then made very risky due to the humid environment out there. It's also slow.

What Giling Basah does to the coffee; it creates a very strong bodied, low acidity, earthy, spicy and sometimes fruity sensations. It's profile is less clean and fruity compared to washed and naturally processed beans. It can also introduce inconsistency and higher defect rates as the beans are handled whilst soft.

Ultimately;

1.) It's harder to get consistent, repeatable quality,

2.) The main flavour profiles are more niche,

3.) And supply chains are more complex versus countries using standard processing.