I skipped them once and my astronomy photos were full of noise, so I always use them now.
I was blending exposures last night and the tedium hit home. It's just like getting everyone on the same page across time zones. Both need patience and clear communication to avoid a mess.
I was never happy with the noise in my deep-sky images. A forum post explained how to take proper dark and bias frames. I tried it out during a clear night, and it really helped. My M81 photo now has smooth backgrounds and clear spiral structure.