Muslims should strive hard to keep their bodies and clothes clean and pure; hence it is better for Muslims to wear leather that is originally permissible or derived from an animal that is lawful.
The Islamic Religious Council of Singapore states the following: The majority of scholars consider pig and all derivatives from it as heavy najis, which entails the necessary purification of seven washings, one of them with a mixture of sand and water, for surfaces that come into contact with pig and its organs. However, the condition is that the surface contact is wet or moist. If it is dry, then no purification is necessary.
Hence, wearing shoes or using things that are made from pig’s organs are not advisable since it runs into possibility of being wet or moist and hence necessitates purification. Without such purification, Prayer (salah ) is not valid.