Why not replace the umpires with robots with all kind of sensors or just a lot of stump cameras with heat sensors, cameras etc..and just give decisions through the Giant screens.
Umpiring is a skill people work hard to acquire and go through rigorous examinations and certification process to reach a level where they can officiate an international Test match. DRS just sends the wrong message to these hardworking people and can put them under a lot of pressure when making a decision. I wouldn't feel comfortable if someone is always standing over my shoulders while I work waiting for a mistake to point it out.
I hope this is a personal view rather than trying to defend BCCI.
The DRS doesn't replace the umpire, it's there to support hem if they make an error (see Matt Prior dismissal). Yes it's used tactically, but it is done so by umpire's too. When 1 team has a review, and 1 doesn't I've seen umpires give decisions to the team who can't review it. Therefor the other team can, making sure we have the correct result.
India used it at first, and on LBWs they were all terrible. It was like they were fresh graduates from the S.Broad LBW review academy. It was selfish the way they used them. It was embarrassing some of decisions reviewed, without even asking the non striker!!
If India only had a problem with Hawk-Eye, why not allow DRS with all but that?