present perfect/past simple

[Lenka]

A: Shall I make us some dinner? It is already 8 pm.
B: No, thanks. I WENT to the denstist this afternoon and my mouth hurts too much to eat anything.

I read this dialog in a practise book of English language. My question is, why is the verb WENT (go) in past simple and not in present perfect tense.
I was taught that we use present perfect to emphasize that something what happened (the visitation at the doctor) has some results to the future or present (I cannot eat) or when telling the news (I visited him and person A did not know it).


A: Do you want a lift home?
B: No, I OVERSLEPT this morning because my alarm clock did not go off, so I need to work late.

My question on this dialog is same exactly. Why is the verb OVERSLEEP written in past simple instead of present perfect?

[ana2005]

I think it's because the action refers to a period of time (this morning, this afternoon) that is already over.

[ana2005]

I think it's because the action refers to a period of time (this morning, this afternoon) that is already over.

(No idea why this has appeared twice. Sorry!)

[uthmaan]

I think it's because the afternoon mentioned is over, and it is now evening or night. The present perfect ("I've been") would be used if it was still the afternoon.