Not always. A well planned walk-in with a long fixed panel and a generous entry can stay dry with no door at all, because the head is aimed away from the opening and the throw never reaches the floor outside. Add a door when the entry is narrow, when the head sprays toward it, or when the room runs cold.
This is the whole question, and you can answer it before ordering anything. Run the shower a few minutes with a dry towel on the floor outside the entry. If the towel comes up damp, the opening is too close to the head you have, or the head is pointed at it. Try it twice, once with the bathroom door shut, because a closed room carries mist around differently than an open one does.
Geometry does most of the work in a doorless layout. A long fixed panel, an entry set well past the showerhead, and a head mounted on the wall that panel protects will keep water inside. A rain head straight down over a bench is the most forgiving arrangement there is. A handheld on a slide bar is the least, because whoever holds it decides where the water goes.
Comfort is why most people eventually add glass at the entry, and it has nothing to do with the floor staying dry. An open entry lets warm wet air roll out along the ceiling while cold room air slides in along the floor. In a New Jersey bathroom in February, that convection loop is felt within seconds.
A panel at the entry closes the loop. Even a half height wing or a short pivoting return changes the airflow enough to notice, without shutting the shower in completely or giving up the open feel that made a walk-in appealing.
Openness, and a little floor space. A hinged return needs clearance to swing, a full enclosure needs a threshold or a curb where a curbless layout had none, and both add a surface that has to be squeegeed and wiped where an open panel simply drains. A curbless floor complicates it further, since there is no lip for a sweep to close against and the glass has to stop just short of the tile.
There is a middle position worth knowing about. A long fixed panel plus a short pivoting wing at the entry blocks the draft and the stray spray, folds out of the way when it is not needed, and keeps the shower reading as one open space. That configuration is what most people actually want when they start asking about this.
Wide enough to walk through without turning sideways, and far enough from the showerhead that spray never carries to it. Those two requirements pull against each other in a small bathroom, which is why panel length and head position get worked out together at the design stage rather than one after the other.
It reduces the draft, but it does not stop it. A fixed panel blocks water traveling sideways and does nothing about warm air rising out of an open entry while cold air slides in underneath. If the complaint is cold rather than wet, the answer is closing the entry, not lengthening the panel.
Bring photos and a rough floor plan to the Lodi showroom and someone will walk the geometry with you before anything gets measured. Walk-in layouts are one of the few glass decisions where a short conversation up front saves an expensive change of mind later.
