Please allow me to justify the title of this discussion. As you know, there are 39 characters in SSFIV AE. Capcom recently held a character poll (results of which can be seen here: http://www.capcom-unity.com/combofiend/blog/2013/04/02/street-fighter-character-poll-results), and the reason for this was clearly to gain the community’s aggregate reception to the characters in general for all of Street Fighter if they wanted to add new characters as DLC for the upcoming update; or gathering ideas about who should be included in future instalments of the franchise. With 67 characters on there, it’s quite clear than not everyone can be included due to time, budget and balancing constraints. Therefore, by natural selection, the most popular characters will feature in more games (e.g. Ryu is in pretty much every Capcom fighting game).
My proposition is that if the game has fewer characters, not only are tier lists diminished in their utility, but also fewer match-ups and less balancing is required to make the game fair and bug-free. It also makes categorisation easier, and for those struggling to find a character - it’s usually because there are too many, rather than too few - to choose from. I think there are characters in SSF4 AE which are either useless or too similar to other characters.