G'day, mate (or is it "G'die, might?" - coz I swear that's how I hear it when I visit Oz)
Aside from what others have already pointed out, you should also watch some Bollywood movies. The actors speak in a mixture of Hindi and English. My Indian friends say it's called "Hinglish." Many of them were so amused to find out that Filipinos have the same peculiarity as them when it comes to being bilingual.
Btw, in America, the Hispanics have "Spanglish."
In any case, you should come and visit. You'll be glad to know that Filipinos and Aussies also share the same kind of irreverent humor, love for beer and yes, some of us also surf. Google "Siargao" and "La Union" and find out more about the country's top surfing destinations. Who knows, you might find a few fellow blokes over there.
Aside from all the replies above, another reason is that we normally use the local language to put emphasis on a thought, a statement, an idiomatic expression, or even cussing. Sometimes, using our local language seems to allow us to emphasize more on the thought because of how we use that particular statement. Also, more often than not, there is no equivalent for some Filipino sayings just like there are English idiomatic expressions and sayings that do not have a Filipino/Tagalog equivalent.