Why is it necessary to use the colloquialism Oftentimes?

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From what I understand "oftentimes" is a colloquialism derived from the South Western United States, but what I don't understand is why so many authors contributing to this website use the word, when the shorter "often" works exactly the same and sounds more formal.

For example:
Oftentimes, this is the best solution.

Versus:
Often, this is the best solution.

Maybe I'm just not educated enough in Northern American English, but it seems strange juxtapose the formal language used in some articles.

 

[Nova]

why don't you try watching a movie if your bored

 

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why don't you try watching a movie if your bored

I didn't mention boredom, I was hoping to learn something about language.