Novice question about track and field. How come they don't line up side by side during certain events?

Question

Like the hurdles some people seem further ahead and some at the back. Why are they lined up like that?

Answer 1

the inner lanes start farther back because the inner lane is shorter than the outter lane, think about it, its kinda hard to explain, so they measure stuff and set each lane back so that their distances are equal, if its a short sprint race like the 100m they dont face any turns so they start even

Answer 2

The inner lanes are short than the other lanes around the corners. They only do this for the shorter distance events where the runners have to stay in their lanes. Basically the 200m and 400m events.

The kind of do it for the 800 m and 1500m events but not as much because the runners can move to the inside lane.

100m events are straight so they all start together.