Normally, parts of the masonry are cut out and tiled - that's how I know it.
But in a head wall thickness, that's not so easy.
And when I look at my wife's collection, we definitely need more depth.
Well, I only take shower gel and shampoo with me in the shower; deodorant comes in a later step, and toothpaste doesn't go into the shower - neither does shaving gear. Even if I used a different kind of shower gel in the evening than in the morning (or on Sundays different from weekdays), I would always only take the current kind into the "cabin."
I wouldn't want the entire range of beauty stuff lined up constantly in the splash water area. You don't have to play "I'm going to an island and packing in my suitcase..., ..., ..., and ..." in the shower, do you?