Costs and benefits are multi-dimensional

A 64-bit build is not necessarily better in every dimension of cost than a 32-bit build, and users may regard different dimensions as more important. For instance, the hardware memory cache might have a lower miss ratio on a 32-bit build because a pointer occupies only half as much space. Also, using the "x32" code model on x86_64, which restricts process address space to 4GiB but still enables using 16 CPU registers, might compensate for some of the advantages of full 64-bit. Even pointer tagging can be done on 32-bit pointers by segregating allocations that have different tag values into aligned 32KiB or 64KiB subspaces, and associating the tag with the subspace instead of directly in the pointer.