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My "last seen" is turned off for the sole purpose, that some people have an expectation of receiving an immediate reply. There's no need for that sort of pressure for their instant gratification or validation.
 
It sure is a useful feature for most cases to have both parties know if the other has "heard" what each other said. That's a basic feature of communication. But there are times when that isn't desirable, and it's nice to be able to switch it off.
 
I actually recall the day people picked up their phone without looking who it was to decide if they actually wanted to hear that person that particular moment. That tech probably boosted antidepressiva sales worldwide. Probably cost some lives too.
 
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