I totally understand why they don’t use a center channel. I’ve been to audio shows and listened to plenty of high-end 2 channel systems. I know what they can do. A center channel used the way I use it does something they can’t do. It can prevent comb filtering from inter-aural crosstalk. The argument that it’s not necessary is well taken, as I know from experience that the sound can still be great despite the crosstalk. Nevertheless, I prefer to not hear that crosstalk. The only ways I’ve found that work for me to my satisfaction are to either use a divider wall between two speakers that comes all the way up to my face to keep the speakers from playing into the wrong ear, or use an array of 3 speakers that are fairly close together and employ channel summing in the center and differencing on the side speakers. There are other recursive schemes out there that also do a good job of reducing crosstalk but I feel they add issues of their own.
Crosstalk was never an intended feature. It’s a parasitic effect that comes along with only using 2 speakers. People found that they could live with it, and 2 speakers is the simplest way to get some kind of stereo effect, so it became the default standard, mostly out of practicality. Some people have adapted so much to it that they actually add crosstalk to their headphone setups to simulate speakers in a room! I definitely don’t like that with headphones, but to each their own. I do what sounds best to me. Crosstalk isn’t my favorite thing.
My setup still requires that I sit in the sweet spot for full stereo imaging. If I go out of the sweet spot the imaging collapses but centered vocals still stay in the center. More typical multi-channel systems are less sensitive to sweet spot position, but it’s still the best place to be.