Let me first clarify an important distinction between folks who simply enjoy playing with a small head size, and folks who are obnoxious proponents of small head sizes who think they're superior. I can explain the former (you may ignore the latter as they are just.. jerks).
For a rational pro (i.e. who tries to maximize one's ranking), the only factor influencing her racket decision is her performance with the racket. On the other hand, for a rational hobbyist (i.e. who tries to maximize one's happiness), there are many factors other than performance that influence one's racket decision: feel, price, appearance, nostalgic elements, what the racket symbolizes, ability to help you improve, etc.
And a small head size racket tends to score more favorably in these external factors. Hence, it makes perfect sense that more recreational players have fun with smaller frames than the pros.
Of course, the above does not imply that smaller frames lack performance compared to larger frames. Federer is a great counter-example. My argument simply explains why there are more recreational players than pros who play with smaller frames, and why this rationally makes sense.
Wilson Pro Staff 6.0 95.