No need yet. Neither Band in a Box nor Real Band require a lot of memory. Both seem to require a lot of processor computing speed.

So far 64-bit software is there either for family compatibility (products of a suite that use the same libraries) or for usage of memory (working with moving images).

I can see that some software jumped up on the moving 64-bit-train without a need for the improvement at the current time. Using 64bit compilers does not necessarily involve rewriting code, event tho' it does in a few particular cases.

The major advantage of a 64-bit OS is the ability to address more than 4 GB of RAM. But: the Home edition of Windows 7 is limited to 4 GB of RAM. (Haven't checked W8, but I doubt that it behaves different than W7.)

The question is: How many BIAB users have more than 4 GB RAM in their computers and use a 64-bit OS beyond the Home edition?

I still run pieces of 16-bit software on my computer -- and it's main board is prepared to accept 32 GB. I still have no need to put more memory in than the 8 GB I have now.

Desktop; i7-2600k, 8 GB mem., Win 10 Pro, BIAB 2017; RB 2017 - latest build
Laptop: i5-2410M, 4 GB mem, Win 10 Pro, BIAB 2017; RB 2017 - latest build