It used a turtle because Wally Feurzeig, Cynthia Solomon, and Seymour Papert thought this was a good device for teaching about geometry, and Logo was associated with schools (and Lego!!!) because they were trying to change education.

https://en.m.wikipedia.org/wiki/Logo_(programming_language)

Of course, you are also right in that once it has momentum along these lines, people tend to put it in a little box marked “children’s language” and not build on it in a more general-purpose language direction.

A few folks have tried, but like squeak and pharos and so many other dialects of Lisp and Smalltalk, it has never gained serious traction outside of its original purpose.