As far as I can tell, these were the original artists' acrylic paints, having been introduced in this format as far back as the mid-1950s. Somewhat surprinsingly, they were re-branded as Soft Body Acrylics around 2005 and sold in tubes like the Liquitex Heavy Body Acrylics. However, a decade or so later, the small bottles are now back, but a little taller and redesigned to have a nozzle.
The original format bottles were widely-sold. I bought examples from WH Smith’s in the UK; in an office supplies store in Montreal, Canada; and a local art supplies shop in Oxford, England. They were (and are) excellent paints, being heavily-pigmented and ready for immediate use. (No shaking or stirring necessary.) The screw-on cap with flip-off lid made them very convenient to use. There must have been a large number of colours in the range at its zenith; appealing to artists, crafters and model makers. So why did they disappear from the shops?
Probably only Liquitex themselves know the answer. But I suspect that there are a number of reasons. Cheap imports, competing ranges and more specialised paints.
One other point. The selection shown here includes colours that no longer appear in the current Liquitex ranges. To be honest, I can't think of an obvious use for Christmas Green, but Taupe appealed to me as a scenic colour, and Polished Steel is very useful on models and miniature figures. Christmas Green sounds like a craft colour, and Polished Steel sounds like a hobby colour, so I am guessing that Liquitex stopped producing their craft and hobby colours in order to focus on their art colours?