Why do the guys always insist on paying for everything?

Me & my boyfriend were at the mall and I wanted a really exspensive diamond neckalace from Zales that I had been saving up for (it was 2,000$). My boyfriend sees me looking at it and offers to buy it for me. I tell him, 'you're so sweet, but I've been saving up for this for 5 months and I'd like to buy it for myself'. So he gets mad and makes a huge scene in front of everyone, accusing me of not thinking he has enough money and crap. He tells the lady HE'S going to pay for it (very loudly) and asks how much it is. She tells him, 2000$ and 10 cents. Then he gets all flustered because he really didn't have the money for it. I ended up paying for it like I had planned to, but everyone was looking at us and the cashier even checked the money to make sure it wasn't counterfit!

Why do the guys insist on paying!?

And, girls, has this ever happened to you? (not the same situation, but a guy insisting on paying for something that you want to uby yourself)

No rude comments please!
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Just an add-on: This wasn't just a movie or dinner or something, this was a 2,000 dollar diamond neckalace! You can't just make a scene in a jewelry store like that!
Why do the guys always insist on paying for everything?
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