Sorry if that sounds morbid but the COVID-19 pandemic has got me considering this very issue big time of late (clearly got too much time on my hands). I was thinking the other day about past significant people (some of whom I'm no longer in touch with), prompted by worrying about an older friend (with underlying health problems) who I generally see once a year or so (contact is only via email/letter not phone).
So do you and should you? Once upon a time an address book would probably have provided you with all the info you'd need to notify people but not convinced these days.