Why is it necessary to model the concept above?

You did not write the concept, so i will try to answer in a general way.

Why sometimes we really need to model concepts?

Well, sometimes the things are really complicated, or we just do not have the knowledge or tools to fully understand them.

Here is where the models came to be handy, we can somewhat "simplify" the things, and explain them with models.

For example, the movement of a particle as the wind pushes it can be really complex, so this can only be explained with a model.

Now, once we have a model (supported by theory and experiments) we can start to investigating furthermore in the given subject.

So for example, we could model how a given therapy acts on a given disease, and with that model, we could extrapolate the effects of the therapy in a similar disease (for example, testing how radiotherapy acts on a given tumor in some organ, can give information on how the same therapy can act on other types of tumors)

Concluding, models simplify some concepts, which allow us to understand them and work better with them

a physical change is being made.