Your question is a bit hard to interpret and it seems you're asking a few things, but let me attempt to answer.
First, MBB (like any company) recruit where they have historically had the most success. So, they will recruit at school that are both top-ranked and seem to produce candidates that end up integrating well with the company. This is the only priority/concern...alumni do not influence this.
There are strong concentrations of particular schools because 1) Better schools produce better candidates, with a long tail and 2) Regional schools will naturally be better represented (not just because it's logical but because students there are mor elikely to recruit for the local office).
If you studied economics you would understand these forces as the market for lemons (which involves signalling, and asymmetric information)
As such, for Chicago, you better expect that Booth and Kellogg are the best represented.
Your question is a bit hard to interpret and it seems you're asking a few things, but let me attempt to answer.
First, MBB (like any company) recruit where they have historically had the most success. So, they will recruit at school that are both top-ranked and seem to produce candidates that end up integrating well with the company. This is the only priority/concern...alumni do not influence this.
There are strong concentrations of particular schools because 1) Better schools produce better candidates, with a long tail and 2) Regional schools will naturally be better represented (not just because it's logical but because students there are mor elikely to recruit for the local office).
If you studied economics you would understand these forces as the market for lemons (which involves signalling, and asymmetric information)
As such, for Chicago, you better expect that Booth and Kellogg are the best represented.