A couple things I forget in my first reply.
First, this is a multi-national forum. Dektol use may not be as prevelent outside North America. There's also Agfa and Ilford in Europe and I think Fuji markets chemicals outside the USA. Plus, there's the small niche companies that are springing up offering alternatives to the Great Yellow. For example, Phtographer's Formularie offers its versions of improved dektol and many others.
Second, it all depends on what you are trying to achieve. Many participants here are into alternative processes. Second, many choose to mix their own brews. There are many developer formulations out there which used to be commercial products but are no longer commercially available, Ansco 120 and Ansco 130 come to mind.
Even Michael A. Smith, Guru of Azo and Amidol, admits to still using dektol once in a while if he wants a cold-toned Azo print.
Bottom line, dektol has to have something going for it to survive on the market as long as it has. But, the alternatives are out there for the pickins.