"soft" is the default for M3, and lower-end friends. The advantage in specifying them is manifold:

1. You don't need to dig through <code>$ man arm-none-eabi-gcc</code> to find the default.
2. We eliminate any abiguity if gcc suddenly decides to change that default.
3. We become consistent. Before this patch, some Makefiles specified "soft" others didn't. It's just a PITA to be inconsistent.