In terms of a threat-risk analysis, the need of a physical microphone nearby i imagine more than makes up for the risk of an adversary knowing your water quality and electrical consumption as measured by your washer in almost everyones lives atleast..
It also indicates when you are home or out, and likely an estimate of how many people live there. It could collect more data.
Those pieces of data are combined with others, to form a full picture. This device doesn't need to collect it all itself.
Survellance of private citizens is arguably the foundation of the very dangerous problems in societies around the world, taking away freedom, health, peace, and for most, prosperity. When do you stop it?
Yeah, being able to record sounds that the washer makes would probably also enable you to analyze things people say and extract much more information than 'how many people live there' and 'are they home or not'.
But fortunately for us, you need to actually press a physical button to make the machine sing the diagnostics..
the use of customer-central water usage data piques my interest. there's a huge market for selling water and waste data to advertisers and other companies interested in consumer data. This is one of my friend's startups, smartpipes, which is a type of smart sewage pipe - these smart washers remind me of smartpipe (which supports dishwasher waste!): https://www.youtube.com/watch?v=DJklHwoYgBQ
Seems to me like the overhead it would add would way outweigh the benefit for the use case. I wouldn't want to wait an extra 10 seconds for the audio to finish transmitting every time just to prevent nonexistent spies in my kitchen from listening in.
Doubling or tripling the amount of data sent would be negligible over a wire, but an audio protocol won't be as snappy. Then there's the matter of trust/decryption. How are those keys being kept safe? What happens if I lose access?
Everything uses symmetric encryption, including asymmetric encryption. Using symmetric encryption doesn't mean you'd use the same key for every dishwasher, you'd obviously just pair the devices and generate a new key, like everything does nowadays. Also, my dishwasher doesn't use any sort of encryption, and it still leaks.