A reputation of a B-school is usually built over a long-period of time based on various factors which not only include academics but also the quality of students in the program, alumni representation in typical MBA-hiring industries, the strength of the network etc.
Cornell and Yale SOM do not have the same history of producing top-tier MBAs compared to other ivies like HBS or Wharton. Their alumni network is much smaller and quality of students is relatively less strong. The association with a famous parent university doesn't do much to help the case of the MBA school (atleast from an employer's perspective).
As to your question on perceived reputaion, recruiters view Cornell (and Yale) on par with places like Haas, Daren, Fuqua, Anderson, Stern. Rankings between similar tier schools are different in different publications, and moreover, tend to change year over year. As such, I believe most recruiters don't care much about precise rankings.