Balance improvements, including reduction building times.
The more fields/mines you have, the higher your per hour rate will be. For example, building additional mines/farms will increase the overall rate at which you generate ore/wheat. The more mines/farms you build, the faster you will level up.
Fields and mines further from the Settlement are less efficient than those within a Settlement because farmers have to walk further.
Fields, mines and abodes built inside a Settlement do not cost any resources to build however if you build outside a Settlement, it costs resources. The cost is displayed on the empty plots.