I suppose this was an ancient way to ensure genetic diversity and prevent pregnancy losses. There is already quite a bit of evidence that consanguinity leads to miscarriages [0].
Like most people, I use both. Email however has better tooling IMO around high volumes. IM starts becoming a problem once you reach volumes of ~2K messages per day.
As soon as you have few hundred channels or groups in non business oriented messengers like whatsapp, missing critical/important messages cannot be avoided. Skipping certain lists/groups, training your spam filter etc is at least available when you use email.
[0] https://www.nature.com/articles/jp2011115