One easy way to look at is a rock crawler vs. rally. Rock crawlers use lockers and rally uses awd. I4wd basically is awd in the front.
It’s very obvious when you drive the two different machines which has what. Higher speeds the awd handles better with less input needed which is a very good thing for that. Slip between the wheels is desired. Low speed super technical stuff you don’t want any slip or loss of traction, all wheels to act the same.
Will a diff lock drive down a dirt road, yes. Will an awd climb a hill, yes. But extreme either way one would suffer in comparison to the other.
That’s just the truth.