Why do book characters have unusual names?

I hate it too. Especially when they use Cre8iv spellings.

I think it's definitely to make them memorable.

I also think that it's a good way to be sure that no one picks up the book, starts to read the synopsis, sees:

"Ava/Kathy/Jennifer/Emma Smith is an up and coming...",

and the person holding the book thinks "Ugh, no way---I couldn't stand a girl named Ava/Kathy/Jennifer/Emma in school!" and puts the book back on the shelf. 

I think it is (hopefully) to avoid someone saying, "I KNOW you have written this about ___."

I think definitely to make the character more memorable and also to make sure they’re not writing about a real person. If you start writing about John Smith as a truly evil villain then people who read your book will look at every John Smith they know differently. John Smith might get a little upset.
Catherine Coulter has a recurring character in her books that has the same name as my brother. My brother’s name is slightly unusual. My mother wrote to Catherine Coulter and told her that was her son she was writing about! Coulter wrote back to mom and that started a pen pal relationship. Every time Coulter came out with a new book she would send mom an autographed copy.

I checked the Social Security top 1000 name lists for both 1970 (since I consider Robin to be a name used far more then than now) and for 2023. None of those names made the top 1000 list for boy or girl in 2023, and in 1970, while Robin did make the girl's list at number 51, neither Sissy nor Star made the top 1000 names that year, either.

So I imagine that makes them seem somewhat unusual to a good number of people. 

I know or work with someone with all those names except Walk (is Rocky close enough?).

Actually I don't know a Duchess but have worked with Princess and Countess.

It makes the characters more memorable than John, Elizabeth, Mary, and Michael, which is what the majority of the peas would name everyone if baby name threads are any indication. I like dramatic character names, always have. Like Scarlett and Rhett wouldn't be the same as Jane and William.

I feel like those names are at least pronounceable..some of my books, they have very foreign sounding/looking names and I don't know how to pronounce them in my head.. so I kinda have to give them a 'normal' name.. lol

I volunteer at a help agency. I see a lot of unique names.
Regarding Robin-I know both male and females with that name. I have a male 2nd cousin named Robin.

A the agency we have had more than one person named Princess and King (as the first name).

When I was teaching, we had a student whose first name was Precious. Her homeroom teacher declared she was not calling a student Precious, but she did.

I get more annoyed when it's obvious the author didn't give any thought to the name. Like I read a book where a character supposedly born in the 1980s was supposed to be named Ruth (and they were American!). It bothered me the entire book. Another book had a native woman that was called Billie Jo. It takes me out of the story. That said I had an author say she had to change the name of one of her characters in a book because she realized it was the same name as a character in a previous book and she didn't want people thinking this was a sequel (interestingly the first character was Elizabeth and I think she was going to call her second Liz or something, instead she changed it to Alexa, which again didn't seem to quite fit the generation of the character).

Sorry, what I meant was there weren't many babies named Ruth born in the US in the 1980s (that might not have been the case in other countries).  Can't remember what book is was but I read another book where a character's sister I think born in 1960s/1970s was named something really trendy like Kaylie?  While obviously in real life families name their kids things that don't fit current "trends" I feel like it takes me out of the story when that happens in a book.

Two best friends named Bridget and Lucy. One is called Bee by the other friend, but it's not the one who's name starts with a B. That's not annoying or confusing.