The picture is meant to demonstrate
the reason for lockdown in image form, it's not meant to be an accurate representation of what infection rates would look like.

To see real life graphs would mean comparing the infection rate with lockdown, to the infection rate without lockdown, over the same time period, which is obviously impossible to do. We would also need accurate representation of hospital capacities, since flattening the curve just means keeping numbers under hospital capacity, whatever that is.