Your argument is quite solid and sane, IMHO.

Even though I've not come to do any curl development (yet?), I think it makes perfect sense to let libraries do as little as possible - but do those things really well. And libraries can easily be stacked on top of each other - to provide a more specialised functionality.

To take a bit more childish view of this ... I always prefer to see software libraries as LEGO bricks where you combine them to build your master piece. I don't want a single piece giving me something I've been convinced I wanted (like Playmobil) and then get less flexibility to make it my own master piece.