Why does 4.3BSD tip let you set phones from environment but not .tiprc?

[Arthur David Olson]

The 4.3BSD version of "tip" lets you use the environment variables
"PHONES" and "REMOTE" to name alternate phone and remote files to be used.
Figuring I might avoid environment clutter, I put a
	phones=/name/of/alternate/phone/file
in my .tiprc file, only to be chided with an
	access denied
message.

Now before I go fixing this seeming bug. . .is there a good reason for allowing
phones and remote to be set from the environment but not from the .tiprc file?
If you know of one, please let me know by mail.
--
	UUCP: ..decvax!seismo!elsie!ado   ARPA: elsie!ado at seismo.ARPA
	DEC, VAX, Elsie & Ado are Digital, Borden & Ampex trademarks.