Why: I haven't seen a commercial for them in a while.
Answer: Reply hazy. Wikipedia has this to say:
The cereal was introduced in 1958, and was taken off the market in 2006. However, Alpha-Bits re-appeared for sale in January 2008 with a new formulation, touting "0% Sugar!" as a "Limited Edition" cereal. The old recipe was reintroduced later in 2008.But the link to the Alpha-Bits page at Kraftfoods.com goes nowhere.
The More You Know: On Amazon, you can buy a pack of 5 boxes of Alpha-Bits for $49.99 (+ $11.44 shipping). Beware - reviews are mixed.