Yes, it's about that.
Note that these devices run on some internal RC oscillators or similar, so the rate isn't very exact and can drift a bit.
For gyros, high data rates are useful if you need to track very quick motions. Think about virtual reality glasses that track head motion. Lag over a few milliseconds is unacceptable.
Even if you don't need the high data rates, it's recommendable to sample at high rates, then downsample with a filter - just averaging is OK, properly designed FIR is even better - to prevent out-of-band noise (vibrations) from aliasing down to your band of interest. Many IMUs include built-in decimating FIR filters, otherwise you just need to collect all data and do that in your own application code.
The ADCs and the sensing elements in IMUs are also somewhat noisy, and surprising mechanical resonances do exist, hence high BW and proper low-pass filtering is important.
Magnetometers are especially noisy and require a lot of filtration.