I thought the reason was the explicit patent language and lack of license virality.
The Apache license 2 is pretty clear that binary only distribution is allowed, but I think it’s also clear that the assumption is that source is available in some form. Otherwise, why would you care about derivative works?
As is, it would be possible to decompile the JVM code into something resembling source code and then distribute that with or without modification. Which just seems odd to me.
It is in the spirit and the letter of the license to do binary only distribution.
Why do you think so many companies are pushing the Apache License 2.0 over the GPL?