For the dishwasher, I don't have such a need. But for the washing machine, I find it helpful to get a notification when it's done. I usually close the bathroom door while it runs, so I don't hear when it's done and will often forget about it.

Dishes can sit in the dishwasher after it's done for however long it takes me to remember to unload them, but leaving damp clothes in a closed box is something I'd rather avoid.

No, I don't turn it on with the app, and it wouldn't be preferable to do that.

I'm happy to tell you why I like it to save you guessing again: I like knowing when the wash is done via a notification, and also to get status updates when things like salt are low.