Long ago the mountain bike evolved from balloon tire bicycles into capable offroad machines. Or perhaps Gary Fisher invented them (but many people don’t believe in Creationism). Anyways, they started out as balloon tire bikes that got multiple gears and better brakes. The innovators borrowed brake levers and handlebars from motorcycles so that they had enough braking power on those long descents. And thus mountain bikers had flat bars, whereas those dorky roadies had dropbars. That was the nature of mountainbikes, as God intended.
Yet there have been deviants throughout history. Jacquie Phelan dominated early Norba races on a bike with dropbars. And another legend, John Tomac, returned to Norba after racing in the European peloton and used dropbars with some success. Doubtlessly, there have been a number of heathens infected with the northern European disease known as cyclocross who have attempted to bring some road bike items into the sanctity of offroad. But the 1980s explosion of mountainbikes was surely propelled partially by a market perception of the mtb being different from roadbikes, and the obvious visual keys being fat tires and straight bars instead of skinny tires and curvy bars.
The 1990s saw the rise of integrated brake/shifting units and V-brakes, creating compatibility problems that further drove mountainbikes away from dropbars. Shimano’s integrated road levers don’t pull enough cable to work well with V-brakes, and the various cable-pull adapters always fell well short of perfection.
Since the end of the 20th century, SRAM, a company whose lineage is most firmly rooted in mtb technology, created a roadbike shifter/derailleur system that is totally incompatible with their own mtb derailleurs. And the widespread use of hydraulic disc brakes has seemingly widened the chasm. Ah, but there lies the weakness in God’s perfect plan to keep mountainbikes pure. Since both SRAM and Shimano make cable-actuated disc brakes optimized to work with a dropbar lever’s shorter pull, suddenly all manner of MTB frames are vulnerable to dropbar corruption.
Of course, there have been a plethora of enthusiasts putting disc brakes on roadbikes recently, but who’s gonna taint their mtb with roadie filth? Me, that’s who. I’ll follow up later on my project.