I don't think it was due to limited resources.
GIMP development started in 1995. First version of Adobe Photoshop with adjustment layers was released a year later, in 1996. The notion just wasn't there.
GIMP development started in 1995. First version of Adobe Photoshop with adjustment layers was released a year later, in 1996. The notion just wasn't there.
If you still want talking about notions and time, GEGL as the non-destructive backend for GIMP was started by Rhythm&Hues developers in early 2000.
We could have a long conversation about priorities and availability of developers and refactoring and all the reasons resulting in non-destructive editing not yet available, if you like.