Arch support is very important to feet, especially for those with high arch feet problems or over pronations, as this problem always bring them pains. Proper arch support could offer feet properly support, correct the foot position and active gestures, relieve foot pains and other uncomfortable feeling.
Heel cup could improve foot and body balance, this is very useful when sporting, decrease the rate of ankle injure.
Most knee pains and ankle pains are related to the shock to feet, but right now many new high tech materials could help us to make good shoe insoles with excellent shock absorption, these materials could give feet enough time for feet to accept the impact and the impact was decreased a lot when it delivered to feet.
We all know that if the pressure focuses on one point, that would be very hard, but if we could distribute the pressure on large area, then each part would feel little. It is same the pressure to foot. Some fat people could feel very bad at foot and ankles, because they are over-weighted and the weight can not be even on foot.
If the air in the shoes can not be circulated, and if the bottom of foot can not breath, there probably lead some problems. Bacterial could increase and foot maybe suffered from the sweat all day long.