Model is the Front Gate to your code

Treat model as the front gate to you Code House. A guest/newcomer to your house would enter through the front gate, will be welcomed by the garden on both sides, will be guided by the road that takes her to the main door. And he will ring the bell, will find a drawing room etc. and then you take her around the house.

Contrast that with current state with out of sync, half finished design documents, which are like backyard entry. You don't know which room will u land up in, and you don't know how many rooms you would have to navigate urself till you find someone who can show u around. And all other ways are like entering through windows, roof or chmineys.

This thinking will go a long way in making your code more maintainable. Besides cost benefits (less learning curve and lesser bugs), it has soft benefits like developer morale. This motivate s developers to innovate. So, use Models whereever possible just to organize code, just to create that front door.