Some people are allowed to wear footwear inside. On the other hand, most of the Temple authorities display a board which says “Footwear is not prohibited inside the temple premises”.
Did it ever cross your mind as to why is footwear not allowed inside a Temple.
There could be many other reasons too. Another reason could be the expression of respect. It is like a European taking off their hat. The removal of shoes in a place of worship is considered as exhibition of humbleness in the Sanatana dharma tradition. We must respect that tradition. We remove shoes before entering a Hindu temple in order to pay appropriate respect to the deity within the temple.
You should feel home and comfortable inside the God’s abode (devalaya) or place of worship which is considered holy. Our body cells should experience the direct contact with such holy place and should feel home, relaxed.
That could even randomly invoke the memories of our ancestors who spent their life in building such temples in the cells. Those memories and your devotion together develop an emotion-of-sort that you would get inside the temple. So in old traditional temples you are required to remove upper cloth (your shirt and t-shirt) and wear only Dhoti. So it is not just footwear that needs to be removed. If you don’t like such things, well, nobody is compelling you to go to temple.
Most shoes are made of leather, which is against the Hindu provision of “ahimsa” or nonviolence. And even though Hindus may eat meat today, they won’t disrespect a place of worship by wearing something made of leather to a temple.
Even in Islam and Jainism, Buddhism and Sikhism, it is a practice to remove footwear.