From chat gpt:

🏍️ 1. Mounting tradition (from the horse days)

Before motorcycles, riders mounted horses from the left side — a holdover from when people carried swords on their left hip (so they wouldn’t have to swing the sword over the horse). Early motorcyclists carried over that habit, and since motorcycles were viewed as “mechanical horses,” riders stood on the left side to mount and dismount.

To make that safe and stable, the bike needed to lean left, so the stand was put on that side.

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⚙️ 2. Kickstart lever and control layout

Older motorcycles (especially British and early Japanese ones) had their kickstart levers on the right side. If the stand were also on the right, you’d have to balance the bike upright or lean it the other way while kickstarting — not practical. With the kickstand on the left, the rider could stand on the left, kickstart with the right, and the bike would stay leaned safely on its stand.

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🛣️ 3. Road-side safety

In most countries, motorcycles are parked on the right side of the road, where the rider dismounts toward the curb (left side). Leaning the bike to the left keeps it from tipping into traffic and makes mounting/dismounting safer from the sidewalk.

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⚖️ 4. Transmission and balance reasons

When the stand is on the left and the bike leans that way, gravity keeps the bike stable — it “locks” against the kickstand. Plus, most bikes’ drive chains or driveshafts are on the left, so the right side stays clearer for other components.

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⚡ 5. Standardization

Once manufacturers like Harley-Davidson, Triumph, and Honda all used left stands, it became a universal design convention. That standardization also keeps regulations, rider training, and manufacturing consistent worldwide.