Why does moisturiser need to sink in before applying makeup?

[lovelyjubbly888]

I have very, very dry skin and eczema. One tip I always see is to let your moisturiser sit for a good 10 minutes before putting on foundation/bb cream whatever.
I have tried it and it does help. But what I don’t understand is the ‘science’ behind it. Surely the moisturiser is going to sink in regardless if there is makeup on top of it? I’m just not grasping it 🤔

You don't want your moisturiser and foundation to mix. It would soak in all splodgy.

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I know that's advised, but i have very dry skin and I apply the foundation straight away and it doesn't go splodgy. I use a balm cleanser, followed by a serum, then a balm moisturiser, but the one i have isn't rich enough so i then apply a little bit of a richer one that leaves more of a dewy finish, then apply my foundation. I go back to it after I've got dressed and, with a sponge, just check it over.

I think that's a relic of older spackle-type formulas and powders, where any unevenness underneath would show up. Think of repainting a wall before the previous layer has set properly. But with current formulas where foundations are all loaded with skincare ingredients anyway, I don't think it's necessary at all, especially if you have dry skin that drinks up your moisturiser.