Also found this topic How do Neurons and activations actually work? - #5 by rmwkwok
And these words made everything clear!
However, we never constrain those intermediate (hidden) layers. Meaning that, we don’t have label data for affordability, and we never constrain any neuron’s output to be consistent with the label data for affordability. Without such constraint, we can’t interpret those hidden layers’ neurons as “affordability” or anything else.