Why do girls offer their phone number? I didn't ask for it, she offered and then leaves me on read when I do text?

I was at a bar with a couple friends and we had bottle service etc. started talking to cute girl next to us. We ended up talking and clicking. She had to go so before i had a chance to ask for her number, she offered her number. However i hit her up and we text for a bit and then she left me on read. If you weren’t interested, why gimme your number at all?
Why do girls offer their phone number? I didn't ask for it, she offered and then leaves me on read when I do text?
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