A similar statement could be made for nearly any not-giant private college in central states that does not have a well televised football or basketball team. There are certain subgroups of the general population that are especially familiar with all of these colleges, as well as WUSTL. And WUSTL does get plenty of name recognition among certain subgroups. If you mean, why isn’t WUSTL heralded to the same extent as other schools with similar USNWR rankings, like Brown or UCLA, location and sports are key factors, but there are many other additional factors.
One is WUSTL’s history of need aware admissions. At the time of the Chetty study (published in 2017), only 16% of WUSTL students were not among the top quintile income, which was the lowest among the ~2500 colleges that were reviewed by a good margin. Chetty ranked WUSTL as the worst college in the United States in terms of SES distribution, with more students from top 1% income (22%) than bottom 80% income (16%) . This history has limited WUSTL’s popularity among students who are not high income. I realize WUSTL is much better today and gets a significant number of lower income kids, but this history still influences reputation and popularity among large subgroups of students. For example, in the recent thread at Help the world's pickiest girl correct her misconceptions and build a college list! , a student lists various stereotypes about different colleges and why she shouldn’t apply to them. For WUSTL, her reason was “autorejected for not being rich.”
Another is WUSTL’s lack of appearances in general media among students who are not directly searching for colleges. For example, I can’t recall any fictional character in media ever attending WUSTL or even mentioning WUSTL. I’m sure it has appeared it some media that I am not familiar with, but WUSTL is mentioned far less often than HYPSMC… type private colleges. This reduces the number of kids who are introduced to the college at a younger age, as well as parents of kids.
That said, WUSTL is an excellent college, with numerous great characteristics. I am not surprised by the OP’s decision, and expect she will be happy with the college choice.