It doesn't happen often that I notice, a lot of examples of it end up automatically marked as junk so I only see them if I peer in there for any reason or look

It doesn't happen often that I notice, a lot of examples of it end up automatically marked as junk so I only see them if I peer in there for any reason or look at the mail server's daily/weekly/monthly incoming mail report which will list them. Perhaps your junk filtering is more efficient than mine! It may also depend upon what lists we've ended up on. If only a few junk senders are using the trick, the others deciding it isn't worth it without knowing there is a catch-all isn't worth it and deciding working out there is a catch-all with sufficiently few false positives is too much hassel, then it is quite possible it only happens to some of us. It could also be that some people have done it to pad out email lists they sell, and so most of the others aren't really using the trick but just parroting the list they have bought. Again, this would explain the issue only being seen by some. My domain is a .net that has been active for about 23 years at this point, so compared to newer domains its presence in spam mailing lists will have been subject to more fads in the junk industry over time.