Banning something does not always fix the problem of its use. Per the article, there's a sizable sporting contingent with competitions being common. If there's money and fun in it, it doesn't go away just because the government says you can't do it anymore.
The article also mentions lots of local bans, and that the practice remains popular regardless. Motorcyclists still get cut by the lines, sometimes fatally, but there isn't any formal data collection to categorize the lines as a cause of death.