Why is the 5′ end of DNA a monophosphate?

According to my textbook:

While the 5′ end of a DNA strand is typically a monophosphate, the 5′
end of an RNA molecule is typically a triphosphate.

Source: Biology: How Life Works, 3rd Edition

How do we know the 5′ end of DNA a monophosphate? I understand that…

• DNA and RNA synthesis cleaves nucleoside triphosphates into nucleoside monophosphates to form the sugar-phosphate backbone.
• Necessarily, the first nucleotide will have three phosphates intact.

What I don’t understand is why DNA doesn’t have a triphosphate on the 5′ end like RNA. How does that happen?