It seems that 20 or so years ago, you had no problem finding a fair number of what were usually referred to as "mule ear Oncidiums". I think that they have finally separated these along with the "rat tail" Oncidiums to the genus Trichocentrum. It seems such a shame that this group of beautiful orchids have fallen out of favor. They are relatively easy to grow and they provide an exceptional show while blooming. Many are still commercially available so maybe they will once again become common place in collections. Many of the intergeneric crosses using the species of this group produced interesting but sterile hybrids which resulted in a dead end in a breeding line. Maybe this is why dealers stopped handling them. The pictures are of Onc Florida Gold 'Merkel'.
They are out of favor because commercially they are too slow growing. So growers raise Phalaenopsis or other fast crops. It is all about cost per square foot in a greenhouse. The mule-ears (Lophiaris) as as slow or slower than a standard Cattleya. For the general public Oncidium intergenerics from plug nurseries in Hawaii are equivalent but a whole lot more profitable.
I really hadn't thought about it from the commercial grower's point of view Eric. I'm sure that is probably a major factor. However, it seems to me that there are a number of other genera like the vandas and such that are also somewhat slow growers and their popularity seems to be growing instead of dwindling . Is it that in the case of vandas that dealers can command a higher price? I imagine that commercial orchid growers are probably like me in that they would like to give up eating 3 meals and sleeping in out of the cold rather slowly. It's sad that lust for money not only affects our global economy, but what orchids we can grow.