Why do people try emotional manipulation on others? It only works on the weak (easily influenced) & annoys the strong (not easily influenced)?

I have just begun dating this guy and he is trying to be emotionally manipulative. Making comments like 'do you really miss me', etc. when I say I do and such

This comes from the fact we couldn't meet up this weekend - like he kept pushing - due to my having hurt my leg & a medical issue with one of my parents I'd had arranged months prior. We merely rescheduled to this weekend instead.

Like I said we've just started dating, it's far too soon to develop any serious / strong feelings. I do like him quite a bit & I'm not dating others (I'm a one guy sort of gal).

But as someone who isn't emotionally "damaged" or "weak" (by this I mean I'm not a doormat partner) his attempts at emotional manipulation are more irriating than endearing.

Why do people try emotional manipulation on others? It only works on the weak (easily influenced) & annoys the strong (not easily influenced)?
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