Why do people immediately think chaos when they hear anarchy?

Because anarchy would immediately lead to chaos.

80's and 90's punk culture.

This is what merrian-webster says:

1

a: absence of government

b: a state of lawlessness or political disorder due to the absence of governmental authority

c: a utopian society of individuals who enjoy complete freedom without government

2

a: absence or denial of any authority or established order

b: absence of order : disorder <not manicured plots but a wild anarchy of nature — Israel Shenker>

These definitions seem to contradict in terms of connotation. It may just be that people do not understand your definiton of anarchy. Maybe you should explain it to them.

Without cops I would consider it necessary to take it upon myself to enforce traffic laws, or in the absence of laws, sensible driving, and since I don't have a gun or a car I would probably do that by throwing rocks or shopping carts at cars that are speeding or running stop signs, and that would probably not go well.

Because in the past sometimes anarchists assassinated corrupt political leaders or took violent actions against state repression which unfortunately made them associated with bomb-throwing terrorists.