Who ever said it wasn't a good idea?
Nimzo Indian Defence

The idea for white could be to get in e4. For example, after 1,d4 Nf6 2.c4 e6 3.Nc3 Bb4 4.Qc2 O-O then 5e4 is possible. If white doesn't want to sac a pawn then after BxN it's necessary to double the pawns. 5a3 BxN 6pxB could be a sneaky attempt by white to get into some 5e4 lines whilst avoiding others. Beleive Capablanca played it against Ragozin in Moscow '36. A recent book on Capablanca's games described it as a positional masterpeice in exploiting space advantage as if Kramnik travelled back in time or some such gushing praise.
Just goes to show there exists some 1d4 players who are not so obsessed with avoiding pawn structure weaknesses as most 1d4 club players are.
Does anyone know the reasons why it's not a good idea to capture the black bishop after the knight exchange with a pawn instead of the queen?
In return for a doubled pawn you could get rid of later, you have a semi-open file, your black bishop and queen have a lot more breathing room and they've traded off one of their bishops.