The justification in the RISC-V spec is that it might make porting some software easier. They also say that unaligned loads/stores may be non-atomic and take mu

The justification in the RISC-V spec is that it might make porting some software easier. They also say that unaligned loads/stores may be non-atomic and take much longer than aligned accesses -- allowing firmware emulation on simple implementations. The current atomic extension doesn't allow unaligned at all -- though I think there's an extension to allow atomic unaligned accesses in the works.