The short answer is that they can, but a properly designed and installed frameless shower door should manage water effectively during normal use.
Here's what matters. Frameless shower doors don't have the continuous metal framing and seals you see on traditional enclosures. Small clearances are necessary for the door to move, and some designs use discreet sweeps or seals to help control water. That means a frameless enclosure isn't necessarily watertight, especially if water is sprayed directly at an opening.
Most water problems come down to the shower's layout. The direction of the showerhead, the slope of the curb, the position of the door and the way the glass meets the walls all influence where water travels. A curb that slopes toward the bathroom, for example, can create a problem that no amount of beautiful glass will solve by itself.
That's why final measurement involves more than checking the width and height of an opening. The surrounding conditions need to be considered before the enclosure is fabricated.
The objective isn't to seal the shower like an aquarium. It's to design an enclosure that works with the bathroom and keeps water where it belongs under normal use.
A good-looking shower door matters. One that works properly matters just as much.
Ed | Shield7