Those apps have voice and video features, so it makes sense that they'd request microphone access. (And iOS lets you disable those specific features if you want

Those apps have voice and video features, so it makes sense that they'd request microphone access. (And iOS lets you disable those specific features if you want.) iOS also shows an indicator if an app is using the microphone. This is true even for built-in Apple apps like Voice Memos. There's no way to surreptitiously record.