Not really sure if it's the correct term but is it ever going to be implemented for those who live in 3rd world countries like me? I live in the Philippines and would like to see use the currency "PHP" sooner. I don't know if this has been in talks before but I am going to bring this up anyway.

They will probably continue to focus on "bigger" currencies, to open up bigger markets as they grow. Steam has been around a lot longer, and has been dominant for so long that they've already got support for the big markets out of the way, and can afford to add support for the currencies of smaller nations; GOG only started adding support for languages and currencies other than English & USD (respectively) a couple years ago, and they've mostly focused on EU and major English-speaking countries.
With regards to currency, I assume they'll go after more of the Latin American countries before long, and past job listings show that they've been looking into China, as well. The Philippines are (is?) probably a ways down the list.

Anyway, feel free to vote for it in the Wishlist, as that can't hurt. :)

Alright, thanks for the reply! :)

Do regional currencies have any functional benefits, aside from slightly better conversion rates?

Some banks can charge fees for buying in foreign currencies. Although often it's in the region of few %, there are cases when there is a minimal extra fee. If for example the bank adds 1.75% with a minimum of 5$, then it's no biggie if buying something for 500$ but it does double the price of a 5$ GOG game.
Some (very few thankfully; but I've come across cases) banks even not allow transactions in foreign currencies altogether.

That said, when most people ask for "regional currencies", they're actually asking for "regional prices" and honestly do not recognize the difference between the two. What they want is to have the game much cheaper, like on Steam.
When GOG does introduce regional currencies but without regional prices, they still wonder "why are games on GOG more expensive than Steam?".

Do they have better conversion rates?

GOG conversion rates are usually slightly closer to the real/mean conversion rate compared to what banks would offer. That said, GOG updates its rates less often (weekly? monthly?) which might or might not work in your favour, and GOG rounds its prices to x.99 or x.y9.