Mould needs two things: spores, which are everywhere and always will be, and moisture. You cannot remove the spores. You can absolutely remove the moisture – and that is the entire game. A bathroom that dries within minutes of a shower cannot sustain mould growth, no matter how little you scrub.
Every shower releases litres of water as steam. In a bathroom with working extraction, that steam is outside the building before it condenses. In a bathroom with a dead, undersized or roof-venting fan, it soaks into the coldest surfaces – ceiling paint, grout, silicone, window frames – and the colony you killed last month rebuilds on schedule.
This is why mould treatment alone is a subscription, not a solution. Kill the mould without fixing the airflow and you have booked yourself the same job again in six weeks.