Because that opener places you below the other person before your argument has even begun. Not because politeness is wrong. Because the first sentence sets the hierarchy of the entire exchange.
"I understand your concern, but the numbers show..." says something specific to the room: I am reacting. I am managing your challenge. It hands the other person the higher position before you've said a single fact.
Now take the exact same data, one change to the opener: "That is exactly the point I want to address." Then the numbers. Same facts, same evidence, a completely different position in the room.
The room sets your authority position in the first three seconds of your answer, before the evidence, before anything you prepared lands. Your first sentence is not a sentence. It is the frame everything after it runs through.
The next time you're challenged, catch yourself before you open with an apology disguised as empathy. Lead with a frame that puts you on equal footing, then bring the evidence. Try the swap and watch what the room does.
Framing like this is one piece of what PACE rebuilds inside the Live Loop, using your own real meetings. Take the two-minute self-assessment to see if this is your specific pattern.