Are you talking about a HTML5 datepicker input or a framework/library datepicker e.g. jqueryUI ?
If you're talking about the former - perhaps you need to realise that the user may not be using a browser that displays the datepicker in the way that you think it does. Therefore the user needs a textbox of some description to enter the date. A library picker on the other hand should display in the manner you need, unless js is limited/off.