a grammar question

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Hello

I sometimes hear so many English speakers say "being" instead of "is that."

Here are some phrases: • "the point is that" vs. "the point being" • "the reason is that" vs. "the reason being" • "one thing I noticed a lot is that" vs. "one thing I noticed a lot being"

Please tell me why English speakers say "being" instead of "is that"? What kind of a grammar structure is it? I would like to know more about this structure. Where should we use this structure?

Thank you for taking the time to help me. Best