I'm not familiar with this app, but a service lets you do potentially nice things like cross device sync and sharing observations with trusted others.

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3form 2 days ago | parent [-]

I'm assuming the question should be further refined to "why does the service need to know the data". The things that you mention could be done with the service only having the encrypted blob.

	▲	array_key_first 2 days ago \| parent [-]
		Encryption is more work than not-encryption, and most software is optimally lazy and barely functional. The main goal of the developers is to make the app almost work most of the time, and not crash too much or be so inconvenient that users delete it. Anything past that is extra, and businesses don't pay for extra.