References were made to Pontiac’s hayday in the 60’s and 70’s of being a sought after muscle car and symbol of America’s love affair with cars. Buick on the other hand has been a poor performer for a long time with GM and struggles to sell 100,000 cars in the Unites State a year. So the reason why Buick still exists…China. 

It turns out that in China, owning a Buick is a symbol of status and sales there are doing quite well.
“More importantly, there’s China. “Without China,” said GM design director Ed Welburn, “there’d be no Buick.” Through a series of historical flukes, Buick is the nameplate that General Motors wound up building in China, where it’s now one of most popular brands in one of the world's fastest-growing markets.  Killing Buick in the United States would irreparably harm the brand in Asia, GM officials believe.” - MSN