Speakers are different than headphones. With speakers you have a sweet spot, if your head is not in that sweet spot than the stereo image is blurred in someway

Speakers are different than headphones. With speakers you have a sweet spot, if your head is not in that sweet spot than the stereo image is blurred in someway and that image is affected by room reflections, the stuff in the room, volume setting, etc. This is why headphones are common for mixing, when you lean over to adjust that preamp you take the stereo image with you instead of moving out of it. We are more tolerant of speakers in this regard (from the studio standpoint) since the stereo image with speakers changes with your position and is rarely accurate compared to headphones. Midrange is the most important part and it is where the bulk of the information is for most of our music and our hearing, we get a lot more wiggle room in the bass and the highs. It does depend, we don't always need or want that perfect stereo image but it makes mixing easier to have it available.