Computer architecture has two primary goals (Lorin, 13):
1) Provide an efficient mechanism by which to convert high level languages into machine language
2) Provide an easy mapping of machine language into circuits at various price-performance levels
64-bit computing enhances both these goals by increasing the speed with which instructions containing large numbers or addresses are present. Compilation optimization depends on large register sets (a feature of 64 bit computing) and the ability to rearrange instructions effectively (as is the case in RISC architecture). Many instructions to load and store in memory can be executed at once, given sufficient register space.
For some applications, however, 64 bit systems do not observably enhance computer architecture. In fact, there has been heated debate about the necessity of 64 bit processors for day-to-day functions.