Well in C you have non-aligned pointers, because you can have pointers to things that aren't objects and might not be aligned (e.g. individual chars or shorts). In Java everything is at least 8-byte-aligned, you can't store a loose char/short/int on the heap (it has to go in a boxed object that's 8-byte-aligned, though the compiler will do this semi-automatically) and you can't take a pointer to an individual element of an array.

If you applied the C standard strictly, you could use a JVM-style representation for pointers to longs, pointers, and structs that start with longs and pointers, so you could theoretically have an implementation where those pointers were shorter. But you'd have to convert back and forth when casting to and from void* (and char*), and in practice C people expect to be able to cast a long* to int, cast that to void*, and get the same result as casting long* to void*, even though doing that and using it is undefined behaviour according to the standard.