Do not delete your shots in the camera. It does not help much. It lets you understand how consistently you have been shooting. Out of how many shots you achieved the ones you like or the ones which achieved the objective you started off with.
The screen size is too small to give you the correct judgment about the shot. You may miss out something crucial and delete it for no reason.
You may accidentally delete the wrong photograph. Remember, it is irreversible. You cant get back the shot which you deleted by mistake.
As you develop an understanding of aesthetics, there are chances that you may love the photographs you were about to delete today.
Some Images which are not relevant to you may be actually loved by stock agencies as they can see the potential in those images based on the requirement of their clients. They may request a particular kind of photograph and you can explore your own stock to check if it matches their requirement.
Its better to delete the absolute rejected shots on the computer as you can make a better evaluation of all aspects of the photograph. Is it still worth it ? How much space do you actually manage to get by deleting these shots ? As your photography improves, your number of technically rejected shots also reduces and now you are looking at good and bad shots in terms of expressions or aesthetics. This is another aspect as an artist which may change over a period of time, The brief which you have today may not match with the shot which you are about to reject but later on you may have a brief which matches that particular shot. so unless you have a dearth of hard disc space, do not delete your shots without a valid and justified reason.