Why aren't Indonesian dramas on the site?

We don't know. 

The Suggestion thread for adding Vietnam to the database currently has 847 votes and 30 pages of comments.

I think these are the best threads for Malaysia (63 votes, I thought that was higher so maybe there's another) and Indonesia (128 votes).

Why the devs continue to ignore this is a mystery. There's plenty of interest from users, especially for adding Vietnam.

From the FAQ: 

"Once we have a large number of entries from these countries, we will consider adding more countries to our database. Our goal is to have a complete database for the countries we do have."

Singapore was added in part because there were already Singaporean titles in the database but listed under China, so I guess that makes sense. And it can serve as the current thing to point to as to why the devs continue to ignore interest in Vietnamese, Indonesian and Malaysia titles. But there's been no transparency.  We don't actually know.

Has the inclusion of Singapore added a lot to the mods' workload? Is there a massive backlog or are a few contributors trickling titles in? Again, we don't know.

I know it's their site and the devs are entitled to do whatever they want with it. For all the effort some of us put in to help improve the database, we'll only ever be guests in their house. But the conditions they laid out in the FAQ have been met for adding more countries.

There are a large number of entries from the seven countries and what remains of the gaps in the database can continue to be filled in by obsessives like myself as we come across them. 

If there's another reason not to, then some transparency would help.

 TimiZero:

To be honest I personally find this Singapore addition as rushed and seemed like only to shut few noisy BL fans some time ago, as well as to add more of the future China produced BL disguised as "Made in Singapore".

The addition did appear to be rushed, but what I saw wasn't related to BL. The devs put enough brakes on BL-related content I cannot see them adding a country just for that. (Articles about directors have to include at least one het title. They refuse to add GagaOOLala as Original Network or Where to Watch even though Gaga had an account and wanted to contribute. More.)

BL titles being added in more quickly is probably just a matter of a large fanbase and well-organised sites to gather the necessary information from. If those sites are accepted as a source for verification too, that will likely speed up the mods' turn around time for approval since it all be in one place. It can't be compared to a new user who seems to have taken every short cut to save herself time and has made several mistakes along the way, like not changing the year from series 2 for 3. (I was following all of that as I had offered twice to help her learn how to make submissions likely to be approved.)

 TimiZero:

That's why adding Singapore was kind of inviting more speculations than answers, because we all know which country lead the voting before this and Singapore was not even 2nd place. 

Agreed. Just tell us why. That's all they need to do.

The anime project seems misguided to me. Just let myanimelist serve that need rather than take on duplicating info for tens of thousands of titles. Maybe they're chasing money or something? I don't know. English-language information for more SEAsian countries would fill a gap we don't have a good alternative for. I'd love a sister site that's just SEAsia.  Would still use MDL for Japan of course :)