pro: if the board is being etched it means less copper is removed an therefore the etchant lasts longer.
con: greater risk of electrical contact with anything touching the board edge.
Real answer: it depends entirely on the purpose of the board and its design. There is no right or wrong.
In fact, this is a practice applied so often that there are CADs which when we create a PCB template from their Wizard tools, by default it is added a keepout contour layer internally to the board edge layer.
FvM we apply silicon to fit a piece of plastic that cover the PCB. It is single layer so the risk of contact is less. Thanks to everyone for the input.