Its not the "trend", no. Its been something that's been happening for years, just now getting to be a common thing.
So many people want Retics and Burms, but not everyone can handle a 15' - 20' long snake.
The Dwarf Retic happens naturally, in the wild. They are a specific morph that are found on certain islands, in southeast Asia. People just started breeding them to mainland names bit shrinking everyone down, a bit.
We even have Super Dwarves now...the males won't get any bigger than 5' -6' and females around 6' -7'. Perfect for a keeper who wants a retic but can't handle the mainlands, due to safety concerns, state regulations, etc.