Why do some rainy climates have almost no thunder even when storms are frequent?

Lightning and thunder are most common in deep convective clouds where ice particles, graupel, and supercooled droplets collide and separate electrical charge. In some coastal or tropical maritime climates, rainfall is frequent but the clouds are comparatively shallow and stable, producing drizzle or gentle rain rather than electrified thunderstorms. Without strong updrafts and a substantial mixed-phase zone high in the cloud, lightning formation is less likely. That is why some wet regions can be rainy for much of the year yet experience surprisingly little thunder.