Or as possibly for "attitude adjustment", or so I'm told. The end that attaches to the bike is of a "quick release" design...just give it a tug and you're good to go.
I saw a kid grab hold of one at a rally one time as people were slowly riding down the main drag. I'm pretty sure that was the last time he thought it was cool to have a long tassel hanging from his handle bars.
Left side. Lanyards like that are for decoration only.
Some people like fancy paint, some like chrome, some like stitched seats, some like white wall tires, some like blacked out engines, etc etc etc.
To each his own.