A few of my friends aren't doing straws. They are extended breastfeeders, so maybe that's why they're so against anything other than a real cup?

I pump all day, except for in the morning when my daughter will nurse, so at this point, nipple confusion isn't on my radar.

Any other reasons why using a straw would be "bad"? I'd like to start offering my baby sips of my green smoothies, and letting her drink water from a kids cup w/ straw.