Adding a slide/velocity effect to a non-rigidbody2D object

I have the following code that tries to reproduce the velocity effect:

     if (Input.GetKey(KeyCode.A))
     {
         transform.Translate(Vector2.left * velocity * Time.deltaTime);
         velocity++;
         if (velocity > maxSpeed)
             velocity = maxSpeed;
         anim.SetTrigger(moveLeftHash);
     }
     else
         velocity = 1;

     if (Input.GetKey(KeyCode.D))
     {
         transform.Translate(Vector2.right * velocity * Time.deltaTime);
         velocity++;
         if (velocity > maxSpeed)
             velocity = maxSpeed;
         anim.SetTrigger(moveRightHash);
     }
     else
         velocity = 1;

     if (Input.GetKey(KeyCode.W))
     {
         transform.Translate(Vector2.up * velocity * Time.deltaTime);
         velocity++;
         if (velocity > maxSpeed)
             velocity = maxSpeed;
     }
     else
         velocity = 1;

     if (Input.GetKey(KeyCode.S))
     {
         transform.Translate(Vector2.down * velocity * Time.deltaTime);
         velocity++;
         if (velocity > maxSpeed)
             velocity = maxSpeed;
     }
     else
         velocity = 1;

Normally, this should start moving the player with speed of 1 and the gradually build it up to maxSpeed, which is 10. The problem is that the speed remains 1 constant and I have no idea what is causing it. Any help/tips is appreciated. :)