It is food, not a supplement magic
Whey is just dried protein. It has no special muscle building property over chicken or eggs, it is only faster and more portable.
Only if you struggle to hit 1.6 to 2.2g of protein per kg from food; it is convenience, not a requirement.
Protein powder is optional. It is simply a convenient, cheap way to hit your daily protein target of 1.6 to 2.2g per kg of bodyweight. If you already get there with chicken, eggs, dairy, fish, and beans, you do not need it. If you fall short or have no time to cook, a scoop or two of whey is an easy, effective way to close the gap.
Whey is just dried protein. It has no special muscle building property over chicken or eggs, it is only faster and more portable.
If you need 160g of protein and food only gets you to 120g, one or two shakes easily bridges the difference without extra cooking.
Per gram of protein, whey is often cheaper than meat and takes seconds to prepare, which is why busy lifters keep it around.
Only if you struggle to hit 1.6 to 2.2g of protein per kg from food; it is convenience, not a requirement.