Because Dotfuscator Community Edition uses only the most basic obfuscation methods.
Obfuscation is not the ultimate solution. If people want your code, they will get it anyway. Obfuscation just complicates the job.
Just browse through the Dotfuscator releases page to find out which methods will be used in which versions (and believe me, PRO and Suite make your code MORE harder to remake than Community Edition):
Dotfuscator editions