It is because most pigeons we see in cities are rock pigeon and were usually making their nest in cliff, crevases and rock formation[1]. Not in tree. Therefore,

It is because most pigeons we see in cities are rock pigeon and were usually making their nest in cliff, crevases and rock formation[1]. Not in tree. Therefore, they never needed to make such artfully crafted nest since the rock was already providing enough shelter. This is also why they are very adapted to live in cities, because our concrete jungles are actually closer (in their verticality, materials, and relative lack of trees) to mountainous terrain than to a jungle. [1] https://en.wikipedia.org/wiki/Rock_dove#Distribution_and_habitat https://en.wikipedia.org/wiki/Rock_dove#Distribution_and_hab...