Love the rain-repelling side glass... but why doesn't Lexus use it on the windshield?

Also, is there any chance the rain-repelling coating will
on the side glass will wear off? I've only had my '01 RX300
for 15 months...(since 10/00)

 

It's not a cost factor, but a practical matter.

The material/process used on the window would be very susceptible to chips, wear, and tear if used on the windshield. Afterall, look at your regular windshield right now... run your fingernail down it. Feel all the grit and micro-scratches it catches? You front windshield bascially gets sand-blasted everytime you drive. That's why it takes a slightly abrasive glass polish to restore it to a silky smooth finish. The daily wear and an abrasive polish would quickly destroy the repellant properties of the glass.

If Lexus used the rain repellant glass on the winshield, they'd be in a never-ending process of replacing windshields when customers complain about the repellant effect becoming less and less due to wear.

For now, you'll have to settle on Rain-X