not a common feature in proprietary software
Just so you know, the GDPR mandates that you can at any time get a full export of all your personal data from anyone who's processing it in a common, machine readable format. It is laudable though to have that integrated as a feature in the software, rather than jumping through hoops contacting support etc.
I suspect the reasoning for it was more along the lines of "if you're pasting the password, that means you probably saved it in a text file on your desktop or something, and you shouldn't do that so let's stop you from doing it". In reality, it probably didn't work to make anyone store passwords more securely, and only made life unnecessarily harder for people with password managers