Woodwind players would be lost without them, sepecially with the complex modern woodwind instruments. There are so may trill keys and alternate keys... little holes here and there... and the instruments are so enourmous, no one could possibly play them with their bare hands. And where there are keys, there will be pads, something soft and pliable to cover the tone holes much in the way someone's fingers might.
For this reason pads are usually made of one of three major materials, all of which are polymers! Flutes, saxophones, and larger woodwinds (like the bass clarinet and the bassoon) will often have pads made of leather - namely kidskin. Leather is a type of protein. Leather may also be used on clarinets and other reed instruments.
Another mateiral which has been found suitable for pads is cork. It is cellulose, but it has a consistency similar enough to leather to work very well in the same way. And since it is so good at sealing things, it is used on the joints of woodwind instruments as well.
And another major material used in pads is felt, which is a fabric made from wool, another protein. To keep the felt from wearing out or falling apart - as felt can be prone to do - the pads are covered with a sort of tough paper, which has been described as being "a lot like cigarette paper." The paper is - of course - cellulose, since it is made form some kind of wood.
It is not uncommon to find a clarinet or other instrument which has more than one type of pads, depending on what was done at times of replacement or repair. But pads themselves, if the instruments is played often and is well cared for, can last many many years.