1937 French Mercier prototype with 350 cc engine, presumably extant somewhere in a museum. Normal medium motorcycles were eventually found to be fine for courier purposes.
Half-tracks were as far as I know merely a stop gap solution till proper gearboxes for fully tracked vehicles were developed. The early fully tracked vehicles weren't able to steer properly at high speeds, so typical half-track vehicles had a far forward steering axle with wheels, pressed on the ground for grip by a far forward engine. All this "far forward" enlarged the area that needed to be protected on armoured vehicles and the inferior fuel efficiency, high maintenance and low durability of the track part was too much of a burden for non-combat vehicles.
So that's why we can't have cool-looking half-tracks any more. Well, save for a handful aftermarket kits and the Iveco Hovertrack.
edit: How to bicycle in Canada
Modern half-tracks; just not what most think of when they mostly have WW2 half-tracks in mind.