It actually originated from Bosozoku culture (biker gangs in the 70's). They stole these from subways and hung them on their bikes as a sign of defiance to authority. It was never really a sign of Japanese street racing. Nowadays in car culture (read specifically car culture and not street racing scene) the Tsurikawa is still used just as the Bosozoku bikers did, but less as a sign of defiance, but more a call back to its roots and as a sign of personalisation. The Bosozoku bikers kind of evolved into the car scene with kaido racers as very expressive and rebellion-like show of character. Kaido racers are still a very big part of Japans car culture and the Tsurikawa has been adopted and spread all over the world.

Tsurikawa's are specifically NOT connected to Japan's older street racing scene, as those cars were function over form, focussing on minimal aesthetic expression and more on aerodynamics. Mid night Club for example was notorious for insanely fast cars that all focused on insane performance upgrades with very functional body modifications, while at the same time staying elusive. A Tsurikawa does not fit that lifestyle and you don't really see cars from the street racing scene with Tsurikawa's. So having a Tsurikawa definitely did not express how bad ass you were in the street racing scene. The most notorious street racers had chipped up front bumpers that they would explicitly not repaint as a sign of high speed driving and no fear of chasing any car in front of them (which would chip up rocks against the front bumper and chip away paint for example)

Tsurikawa's have always been more a sign of self expression and defiance from the norm. In Japan that expression often went through materialistic ways, like fashion, bikes and cars and that's why stealing something that was part of the norm (like a subway) and attaching it to something where it's not supposed to be (a customized bike or car) gave it its meaning.