The physics
The scale reads the normal force N. That is how hard it pushes on you. Take up as positive. Newton's second law for the person gives:
N − mg = ma → N = m(g + a)
Now take the whole lift: the car and the people, mass M + m. The cable is the only upward force on it:
T = (M + m)(g + a)
Inside the lift, things fall as if gravity were g + a. Going up and slowing down feels the same as going down and speeding up. The scale can't tell them apart. Only the acceleration matters.