about child marriage

I recently found out that prepubescent girls can get married in islam with the consent of their father. I’m confused as to what the reason for this is?

Source is Quran 65:4

This was confirmed in the islamqa.info website as well: https://islamqa.info/amp/en/answers/22442

I asked my mum about this and she says no one really does it nowadays but I’m still confused as to the reason why it is allowed?