Why are CRTs not being sold anymore?

I’ve been looking to buy a CRT online (Best Buy, Circuit City, Inoax.com, etc.), and merchants are not selling as many as they did before. I only found a couple on each site, and they were usually the store-exclusive brands like Insignia. Why is this? Last year they had many, many more. Are they slowly getting rid of the CRT? And if so, why?