As Dave said, forget diesel as a comparison.
They rev lower, because all the parts are heavier. This is needed to handle the compression, and pressure / force.
Diesels have run upwards of 20:1 for years.
They work so differently. They can run higher ratios, as fuel is added after the comprresion cycle, this is why they dont pre det. The fuel is added to an already compressed cylinder, at pressures up to, and around 1800 bar. This highly atomised fuel, combusts when it mixes with the compressed (hot thats what ignites it) cylinder. They also have multiple injections per cycle normally. Pilot 1, Pilot 2, then main injection of fuel.
They also have 'swirl pots' 'bowls' whatever you want to call them, in the top of the pistons, another reason they have to be much stronger.
Anyway, ill stop boring everyone now