I agree, Anna, it can be personality, or maybe fashion personality or savvy?
I admit that I don't have the "eye" you may have or Angie has, and so am probably more likely to step into some purchases that, upon reflection and trying on at home, I decide won't work or are not "me".
The good thing about that is that I often learn something that goes into my pea brain such as, you know this type of hem just doesn't work, avoid that in the future, or the opposite, if you find something like this in the right color, grab it.
Like others have noted, overall that doesn't happen as much with B&M shopping where I can try on multiple sizes, and even go get an item to try on with it. Stil,l some returns occur because I'll find it doesn't go with as many things and so I'll decide I need to be more picky. That means a few more returns but fewer orphans.
Online is hit or miss--I've gotten some of my very best, most fun items that way by trying something new or just because I would not have the stores locally.
Then as noted, size, comfort, fit just can't be judged if it's in a brand that's new to you, or shoes--for shoes I wish everything were available at a DSW where you can put it on and in about a millisecond go, "next"!.
Still, I don't like lots of churning online, so I've become better, I think, at imagining how some things will work or also just trying to resist sales pressure for things I don't really need or want.