Is that an American Style Café as it comesvwith the bill the American Way?

Gratitude included in the bill, hint for splitting the bill?

Last time I visited a Café, the tip was up to me to add to the bill and the bill was not split, but everyone payed for the stuff they had consumed.

Ps: realy, what is it with the tip included in the bill, something for the tax? Or why is it done?