Java was designed to look enough like C/C++ that programmers could move comfortably from those languages to Java. The designers took the opportunity to make things simpler, safer and more productive. I'd guess they felt leaving out the preprocessor met one of those goals.
A good question is never answered. It is not a bolt to be tightened into place but a seed to be planted and to bear more seed toward the hope of greening the landscape of the idea. John Ciardi