Why are the styles so similar

This may be a little conspiracyish... But why is it whenever a cars are redesigned all the cars in that same class from other companies have such a similar chassis or lighting or some other blatant copies from each other? It always makes me wonder if they cross information?

You could say leaks/car shows but then why not just up your game and copy higher end car models ?

Seriously would like to know the reason behind this.