I use chip brushes for non-permanent coatings, like oil or anchorseal - when the bristles don't matter, or I'll be treating the surface after anyway.
The foam brushes are great for single serve applications, but I have a bucket of anchorseal that has a dedicated chip brush that in a bad near by. They're stiffer and more durable than the foam brushes. I like having both on-hand.
Chip brushes can also be good for applying alcohol-based dyes on large surfaces. They flood better than a rag.