Because of the arc, they're not very precise
Is this an argument for the straight edged clippers vs. curved clipper? That probably depends on what you are trying to cut. Without a lot of thought I would have to give the advantage to a straight edge.
Another question: What are the brand names and models of some high quality nail clippers? My wife will shoot you if you lose her prized clippers (they are not all created equal). Go into a grocery store or drug store and the clipper options will probably be chrome plated, pot metal crap.
The same goes for tweezers with a precision edge. One of the kids lost my wife's life long tweezers. I spent an absurd amount of time trying to purchase a contemporary replacement. Many were made with quality material, but lacked the fine precision at the end and the inside flats.
TR