Why do people not consider SIBM/SCMHRD Pune at par with other prestigious MBA colleges despite the fact that they rank among top 20 of India?

Most of the top B-schools in the country select candidates on the basis of CAT and to an extent, XAT. Since the aim of all the students is to get into the old IIMs, so there are a lot of amazing candidates who only sit for the CAT. Since the only way to get into SIBM/ SCMHRD is through SNAP, there is a perception that the best candidates do not prefer to go into these institutions, which is not necessarily true but might explain the public perception. Also, with the introduction of a number of subpar colleges under the Symbiosis umbrella, the value and prestige of SIBM and SCMHRD have declined in the eyes of the general public. 

SIBM and SCMHRD are amazing institutes, but the public might not consider them on par with other prestigious universities due to the above-mentioned reasons.