Anything bright white throws my eyes off completely. But my eyes are very sensitive. A light neutral gray works a lot better as a backdrop for color evaluation or judging b&w print toning, just like pro color viewing booths contain. It's a lot lighter than 18% metering gray. And no, you can't just add black pigment to white paint to get that, because no black paint pigment is really black. It just looks black concentrated. Tone it way down with white, and you'll discover it's either greenish (mineral black) or distinctly purplish (lamp black). A number of other pigments have to be carefully added into it to balance it out.
I once sold the University art museum big batches of their own special light gray paint, which was applied to all their walls. A rather "interesting" incident transpired when the custodian decided he wanted to open and use up the last 5-gallon jug of a previous order, which he discovered in his storage room, before ordering a fresh batch, but didn't realize just how old it really was. Well, when latex paint gets too old, it spoils just like milk. Maybe he had a cold or something, and couldn't smell the full effect. He knew it wasn't fresh, so decided to repaint the utilities room where all the air conditioning and heater equipment was, rather than risk a mismatch on any of the big halls or display walls. Ironically, that was the worst place possible, because all that rancid spoiled smell got sucked into the whole air conditioning system, and stunk up the whole museum so bad that had to close it for several weeks. White shellac primer was put over the bad paint to hold back the smell. I got quite a laugh out of the whole episode, plus a bigger than expected sale.