John Woodgate ) writes:

They are not so easy to obtain in small quantities. They were aimed at
high-volume consumer product manufacturers.

And that leads to another reason why they aren't used.

They are intended for very specific use, in something that will be
built in large quantities with the same design.

But what works for an AM/FM broadcast radio may not be best for some other
use.

I remember when RCA came out with the CA3088 AM receiver on an IC back
in 1971. QST ran an article about it, hinting at big things, yet also
pointint out deficiences. It was intended for a 455KHz IF, so you'd
be stuck with image problems as you started using the IC in the shortwave
range. I think there might have been limitations on the IF strip so
you couldn't run it at a higher frequency. The mixer was a single
transistor, and if I'm remembering, it was used as the local oscillator
also. Maybe okay in a generic broadcast receiver, but not great for
higher frequencies or where better performance was desired. The detector
was built in, and of course, it was AM only. There was no easy way to
bypass that detector, at a time when few hams would want to build an
AM only receiver.

In trying to fit a very specific application, it was lousy for more
general use.

Since then, there have been plenty of AM and AM/FM radios in an IC.
Some have worked better than others for other uses (who can forget
Ralph Burhan describing Loran C receivers using them?), mainly because
they were less integrated, or at least had pinouts in the right places.

Less grandiose ICs work better. The Motorola FM IF strips were at
first just the IF strip, and since they were intended for narrow band
FM, they were better suited for use in amateur applications. Even the
later variants, that added the front end, had the advantage that the
input and outputs were available off-IC so one could fiddle with things
where needed.

And then when you get to the point where an IC is simply taking care of
one stage, such as a mixer, or an IF amplifier, there is infinitely
more use of them in various designs. Of course, they are less useful
to mass marketers, because they take up more space and give more performance
than needed for AM/FM broadcast, so there is a limited market for them.

Michael VE2BVW