Bonnets are still worn by some ladies.
The older, traditional ladies bonnet of the Salvation Army is still to be seen, often on special church occasions.
Amish women wear them and in quite a few areas of the United States, particularly Pennsylvania and along with their very productive farm lands and horse drawn buggies these ladies can be seen wearing their bonnets. Quaker women had bonnets at one time but I think their custom has died out.
As it will be seen, these observances are associated with a simple, but devout, form of Christian worship.
I guess it is only a matter of time before some whizz kid, ladies fashion guy, comes up with a new style bonnet and it becomes the thing every fashion conscious girl or woman must have.
Another bonnet worn nowadays, but only for ceremonial use, is the Warbonnet. This is the familiar, to all western movie fans, as the feather headgear worn by American native Indian Chiefs and some warriors. There are some variations of appearance but the style most familiarly known here was only worn by Indian tribes of the Great Plains. Other areas of what is now the USA had different customs and headgear.
I am sure other parts of the world have other forms of bonnet (but in modern terminology possibly just called a hat) - memory recalls the men of the Himalayas having something similar.