What's with the names in The Color Purple? Why are Celie's husband and the other older men of the book called "Mr. _____"? Why are their last names not given? Thanks!

A simple Google search would have taken you to this --

Why does Alice Walker put blank lines in the book The Color Purple for Mr. Albert? And why did she name the novel The Color Purple? - The Color Purple - Questions & Answers

I think that the novel is about women and the absence of their names may be because of their unequal treatment of women.thanks