The B-32 program was kept alive in case the B-29 program failed. The B-29 program did not fail and we have the B-29 in AH. If we ever have a scenario where we desperately need a B-32, the B-29 makes a great stand in as their performance and capability are very similar.
The B-32 is to the B-29 what the Halifax is to the Lancaster, except that 6,000 Halifaxes were built.