It's simple, efficient, and saves space in memory. While not as big a deal these days where most systems have plentiful RAM, it's still useful on things like embedded devices.

Why waste a whole byte on a bool that has one bit of data, when you can pack the equivalent of eight bools into the same space as an uint8_t for free?

Sure, that works when trying to conserve memory to the degree that a few bytes matter, but the downside is that it's more complex, less obvious.

I've done exactly what you propose on different projects but I would never call it the "best" method, merely one that conserves memory but with typical trade-offs like all solutions.