If you care about opsec, there are many reasons why you would want to use google services: e.g. a hostile actor will have an extremely hard time stealing your emails from Gmail while there's a might higher chance you fucked up a config on your self-hosted setup. Usually, as always, it comes down to smart compartmentalization and using the right tool for the job.
Personally, the ethical perspective is a much stronger reason why to stray away from data behemoths like Google and Facebook. First of all I believe the "usefullness" of many of these services is over-exaggerated: Facebook noawadays is more of a brainwashing service to expose you to "content" that does nothing more than dull your mind and keep you mindlessly scrolling and endless stream of irrelevant advertisements. But even if this isn't the case for all online services, some come at a price I am personally not willing to pay.
We are entering an era of digital slavery where our entire lives are managed by data monopolies that are bound by no rules other than those they create for themselves. I don't care how convenient these commercial services are, if the price is giving up the sovereignty of my data, and the core liberties of my human existence. I make a conscious choice to not be part of this system, and we will all have to face this choice sooner or later.
For more on this topic, I highly suggest Aral Balkan's talk from re:publica this year [1].