When reading the question Front tire and downtube are extremely close, I realized that disc brakes (referring to the assembly of brake disc and caliper, not the brake levers) are always installed on the left side of the bicycle.
Is there a specific reason for this? For the rear brake, I imagine this is so they do not interfere with the derailleur mechanism (on bikes which have one), but it seems the front brake could just as well be on the right side.
Is there a technical reason why disc brakes are always on the left side? Or is it just a common convention?