Moths can rob flowers, which means they cut a small hole inside the bottom of the flower's nectar reservoir and then lap it up. Butterflies can't cut flowers.
I'm not sure where you get that information. Butterflies also feed on nectar from plants, so they do have mouthparts.
On another note, some butterflies (and maybe moths) are cannibals [1] and feed on their own caterpillars:
"Some butterflies don’t only look like horror movie stars, but are horrors in themselves. Milkweed butterflies (Danainae) — the same subfamily that includes the regal monarch — are vampiric cannibals that use clawed feet to tear open their own caterpillars and mercilessly suck the guts out of them. But why devour your own offspring from the inside out? It’s an even stranger phenomenon known as kleptopharmacophagy."
[1] https://www.syfy.com/syfy-wire/milkweed-butterflies-suck-out...
As another curiosity, I believe the death’s head hawk moth (as ‘made famous’ by The Silence of the Lambs) can disguise itself as a bee via scent and just take honey from a beehive.