Just a normal pull-aside curtain is good enough for me, but my sisters and brothers have these glassed wall showers at their homes, so I like the sliding doors too.
I dunno, I don't have a reason why I prefer it as the only reason I use it is so that water doesn't go all over the floor. Plus it's see through anyway, so I wouldn't say I use it as a door of sorts.
If I owned my own home though, and given I had the income, I'd definitely get one of those outside showers on a balcony.