I use a 30-23 (or in extreme cases a 30-27). Tell me. How do I get the equivalent double on a road bike without replacing half the drivetrain?
A 30/23 has a ratio of 1.3 and a 30/27 has a ratio of 1.11.
A 36/28 has a ratio of 1.28 (lower) and a 34/32 (mtb derailer) a ratio of 1.06. Would necessarily make sense to replace a functioning drivetrain to get a double instead of a triple but if you were starting from scratch...
Besides, y'all are missing a point (one presumes; I'm not going to read 300 posts to find out if anyone got it): For those of us that need the wide gearing (for climbing), a triple offers much closer, more comfortable ratios in the 'normal' range.
No, we understand that point. That is a perfectly valid reason why some people prefer a triple. However that is not a reason that one is
necessary or better.