The other guys behind the shoe rental counter agree. Yes, it's really, really hard to bowl a 279. In fact, it's really, really hard to bowl a 170. In fact, you're considered a minor celebrity if you can deliver a consistent 120. Tenpin balls and pins are bigger and interact with one another.
More pins fall down.
Duckpins takes a lot of practice, a lot of skill. The irony is that the lanes are full of senior citizens and young children because duckpins is considered easier than its big brother counterpart. True, it's less work to pick up the lighter, fingerhole-less ball, and, yes, you are given three balls, or chances, per frame. Many duckpin bowling operators put foam rubber or inflatable bumpers along the channels, just to improve the odds. But the extra help doesn't matter.