Why is #'equalp not allowed in make-hash-table ?

[sridhar%tekchips.tek.csnet@RELAY.CS.NET]

 I want to create a hash table in which the keys are lisp objects
that satisfy #'equalp. CLtL does not allow #'equalp  in :test
argument to make-hash-table. Why?
Specifically I cannot have vectors as key values.
For instance  , how can you create a hash-table such that:

	(setf (gethash (setq a (vector 1 2 3)) hash-table) 'foo)
	(gethash a hash-table) => FOO T
        (gethash (vector 1 2 3 ) hash-table) => FOO T.

--sridhar