If you have them in a closet for several years without use some materials will dry up and that is the result. Shoes are not supposed to last forever. Piece of advice, wear them every once in a while, that way the moisture (sweat) of your feet with help avoid this problem.
Point shoes (ballet) and tap shoes are examples of smooth-soled shoes.
Runnign shoes have flexible rubber soles to absorb impact.
Girls' shoes do sometimes have soles. But if they don't it is often because grown ups think it is more comfortable for the girls to be without soles on their shoes.
golf shoes have rubber soles because it is a game played on the grass which needs to have stops at every step as rubber will increase the interlocking of friction, golf shoes have rubber soles
Rubber is commonly used to make the outer soles for shoes.
Wash your shoes.
Yes they do due to how much you walk on them. When your soles start wearing out it's time to get new shoes!!!!!!
soles of shoes are provided with design to increase friction
You need good soles so that they don't wear out too soon, or so that you don't slip. "Good soles" is relative; you need good soles on hiking boots, but not so much on dress shoes.
Yes there are. Tap shoes without soles make the shoe more flexible so you can stand on your toes.
Rubber or leather
to increase friction