Whew. So why is the difference between points not another point? Because a point has no dimension. Or reference. It is 0 in volume or length or diameter. It just sits there at it's coordinates.
So point = (1,1).
Now a vector consists of two points. Or better yet a vector is a direction. With a reference to something. Usually we use normalized vectors with reference to point (0,0)
So you could say since the coordinates of a 2 dimensional vector and a 2 dimensional point are the same, why not use the same object type?
I don't know, good question.
I guess when you are NOT using normalized vectors. Meaning the vector is origin + direction. Then you need more than one set of coordinates. You'd have (1,1)(2,2) for example. This would be a vector starting at (1,1) and ending at (2,2) using absolute coordinates. If you were to use direction then it would be (1,1) and (1,1). Adding 1 to each dimension starting from 1 in each dimension lets you arrive at (2,2).
So I guess the answer is simply. Vectors (non normalized) contain more information than a simple point.
Now after this long ramp up the time delta question is simple to answer.
The normal(ized) time difference is just that, it has no starting point. If you were to schedule a meeting however with a starting point and a duration or time difference between starting and ending time then suddenly you'd need a time vector class. It would have the starting time and the duration. Or starting time and ending time which would make it more complicated.
So the generalized philosophical answer is. If you store more information you have more. And more is not the same as less. So you cannot say more = less. More or less.