I don't understand why not either. But I had two (count 'em!) computer techs make house calls, and neither could get so much as a signal coming through the tape out.
I took the receiver to the electronics store, and the fellow there said the only way I'd get a signal was through the pre-out. I got the signal right away, then after some fine-tuning got to the point where it's an acceptable sound ... but just in mono.
BTW, the receiver has a bank of toggles for the tape side of things, and a bank of toggles for other sources.
For the tape side, the five toggles are:
Play A
Play B
Dub A to B
Dub B to A
Source
If the 'source' toggle is down, it means you're not using the tape functions ... you're over with the other sources (phono, radio, audio signal from TV).
But it's an either/or situation: If you're using one of the tape functions, you can't get at anything else. But if you're using phone (or whatever) the tape toggles aren't useable.
Guess I'll have to settle for mono CD's in the car .... I'm not really inclined to buy a new receiver for this .... Wish I could remember how I managed to get from LP's to cassette's back when I used to do that!