Why is the probability of winning the lottery the same every time?

Generally speaking, it is assumed that a population contains n individuals, from which n individuals are extracted one by one (n≤N). If every individual in the group has the same chance to be drawn, this sampling method is called simple random sampling.

As can be seen from the definition, "the probability of drawing is the same every time" is the premise, and you seem to be mistaken. In other words, a random event with the same probability every time is called simple random sampling. The probability of drawing each time can be different, but it is not called simple random sampling.