Hashtable routines are far easier to write and debug than balanced binary tree routines. Of course there are open source implementations available for both. Bu

Hashtable routines are far easier to write and debug than balanced binary tree routines. Of course there are open source implementations available for both. But I would guess it is easier to write your own hash function than learn to use somebody else's, and easier to learn somebody else's B-tree routines than to write your own. So we live in a world with O(N) hash implementations and O(1) B-tree implementations, for N programmers.