This is basically
due to the fact that the English tense forms express certain concepts
of time and aspects of verbal actions that are not expressed by means
of verbal forms in many other languages.
choice of the tense form in English depends in most cases on whether
you see the action as something complete (simple
form) or in progress (progressive form), as timeless (Present
or limited in time (Present Progressive), whether the focus
is laid on the activity or on the result of the activity, etc.