Here's a quote from a Shimano engineer on the origins of Rapid Rise.
"We originally designed the reverse spring for the Nexave group to make shifting less complicated," Boehmke said. "But it worked so well we applied it to the '97 XTR group. Our racers (like Kirk Molday, Alison Dunlap and Dave Wiens) love it."
So it did come out of Touring /City bikes.
But it ended up in a lot of groupsets. Vintage Dual Control road levers are supposed to be optimized for RR, but some XT versions exist. I'm not sure what brakes they work with.
It came out so the shifters on 3x bikes would both work the same direction. But on 1x it allows downshifts when stopped, and multiple gear downshifts without pedaling. Good for close quarters riding or unexpected situations. You do have to pedal it into gear, either before or after stopping.
I blew up the Deore 3020 Acera derailleur on the Ebike (native support for 1x8 11-40t cassette) It didn't last a month. So I'm back to XTR Rapid Rise there.
Since it's a 2004 bike I'll mention some other upgrades I did at the same time. I used Jagwire Elite Link cable set, and ran 3/16" steel automotive hardline for the internal frame section to eliminate unsupported cable housing flapping around inside the frame. The prestretched Jagwire cables required almost no tuning to get the shifts right. So solid metal cable housing from end to end. The teflon liner from JW fits inside the brake tubing, 5mm brake housing cable ends fit over the cut ends. I've used this in external sections also, such as up suspension fork legs, and down the seat stays for HT bikes with cable disc brake conversions. It really helps the responsivness of the controls. You can really feel what the brakes are doing instead of feeling the cables flapping around. FWIW I'm getting modern braking performance out of Avid (not SRAM) BB7 brakes with metallic pads, and Shimano Icetech alloy core rotors.