Why time is not a vector quantity even if it always directed from present to future?
because it can described only by its magnitude
To attempt to put a finer point on it:
-- In the case of any true vector, its 'magnitude' and its 'direction' are physically
different quantities. They have different physical dimensions, and either of them
can change without changing the other one.
-- But the 'direction' of time is not really a direction. When you say that time
is always 'directed' from present to future, all you've really said is that no matter
what point you measure from, the magnitude of time is always increasing.