Why have Phantom Dancer when some champions (barring explicit mention) can phase when walking anyway

Hello,

I've seen some weird stuff where I get trapped in minions and other champions because they can "walk through" my position causing me to stutter step through them like I'm getting jiggy with it. They don't have a mention of phasing through anything in their kits yet they do it through me. Not in knockups or other misplacers, but just walking.