Well, Scanner was in 1.5, so the proper question would be "who wants to use 1.4?" Reading through the posts here on JavaRanch, the answer is obviously "many people".
As to why someone would use Java 1.5, well, not all operating systems have a released version of Java 6 yet, OS X being the most prominent one.
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Also a lot of code was written when 1.4 was the latest JRE. Even if newer developments of this code are being written in 1.6, people are not going to want to rewrite existing, correctly functioning code just to use a different class. [ April 04, 2008: Message edited by: Joanne Neal ]