How old is too old for a pacifier ?

So I was scrolling down my Facebook and came across one of my Facebook friends who had posted pics of her 3 almost 4 year old daughter, riding a bike with a pacifier in her mouth. Now to me that's Wayyy to old. Once they have a mouth full of teeth, a pacifier should no longer be in the question. You can obviously see her teeth are being affected by sucking on it. I know moms are gunna do what they want and raise their kids how they want. But what do y'all think?