What do Filipinos gain by being proficient at Tagalog? The short answer is NOTHING. There are no bodies of knowledge of consequence articulated in Tagalog, no essential technologies documented in Tagalog, and no pathways to a lucrative career paved with Tagalog.
Korean, on the other hand, like other languages spoken by societies with rich and extensive traditions of scientific, technological, industrial, and economic achievement opens doors for its speakers. Like English, Japanese, Chinese, German, etc., it serves as a pipeline to a pool of minds that collectively have delivered RESULTS to their respective societies and countries.
When it comes down to a choice between spending time learning Tagalog and using that precious resource getting on top of Korean, the choice is clear as to what the winning path to take is.