The main convenience of it is when deriving formulas, rather than when applying them. With all the constants set to 1, they don't need to be tracked throughout

The main convenience of it is when deriving formulas, rather than when applying them. With all the constants set to 1, they don't need to be tracked throughout the formula, and can be put back in at the very end by looking at the units. Sprinkle the appropriate (hbar*c) or (mu0*epsilon0) at the end, and then you get your constants back.