The short answer would be: I kept writing a code that spawns goroutines, that read from a channel, do some processing and write results to another channel. Add some wait/err groups to this and we'll get a lot of boilerplate repeated all over the place. I viewed this as "channel transformations" and wanted to abstract it away. When generics came out it became technically possible.

Surprisingly, part of my inspiration came from scala (which I haven't touched since 2014). Back then Scala had transformable streams and the "Try" typethen.