Those are just automated feedback reminders which we all receive, it annoys some, though you can deselect receiving them in your Site Preferences , and some members don't mind being reminded.
End of the day, feedback is and always will be, entirely voluntary for both parties, and it's a fact that fewer members on both sides, are leaving any.
One tip if I may, never send a message to a buyer to leave you feedback, as you may receive some, you didn't wish for. For example, a buyer received your item that they're not happy with , but do not wish to leave negative feedback so leave none. Then, along comes your message to leave some, so they think....'Well OK as you're asking.....!' and so a negative feedback is left.
@smith9081