Many of the products sold claim to do more than one thing. You have scrubs that will moisturize your face. Cleansers that also act as toners. Moisturizers that have sunscreen in them. And almost every other product will also protect you from oxidative stress, among other things.
It makes sense to use as few products as possible on your skin. After all, they are all chemicals. The way to do it is to use 2-in-1 products just like hair shampoo and conditioner often come as one product.
The real question is, which is the right combination. Take cleansers and toners for example. Both tend to try your skin. And if you use them both daily, this can quickly become a problem for your skin. I personally believe that toners should be used separately. This way you can skip a day when your skin gets too dry.
Many toners, scrubs, and exfoliants also claim to moisturize your skin. This can be the case, but it can also be a sham. Some of the products have a high concentration of glycerol (glycerin). This acts as a humectant and also as a smoothing lubricating ingredient. Humectants are molecules that bind water from the surrounding. It means that water is drawn from deeper layers of skin to the superficial stratum corneum. And because it also makes your skin feel smooth under your fingers, this can falsely be regarded as “hydrated skin.” But in reality, they use chemical properties and human psychology to mislead us. The truth is that your skin can get even dryer after using these products.
Where I do recommend using combination products is moisturizers. It makes sense to use one with sunscreen in it. Especially if you live in a sunny climate. Excessive sun leads to premature aging and is a skin cancer risk factor (to be more precise – the ultraviolet (UV) radiation) . Then again if you happen to live in a country where the sun is as rare as a unicorn, then you might want to forgo this advice.