I have my own media server, because when netflix removes friends, ill still be able to watch it. sure that means i have to buy the box set of friends for like 100$, which is 10 months of netflix into a single show. but i never have to worry about that going away. I'd rather have a raspberry pi with a webcam with motionEye letting me monitor my house than feeding private data into a company a dont trust.
This is also a hobby for me that has benefited me in my job on multiple occasions, and I only do it for services that I'm ok with downtime on (I've outsourced my email even though that's the data I would love to control the most, I'm not going to mess around with downtime on that). I absolutely wouldn't recommend any of these things for my grandma.
Also, "unpaid system administrator job" can be a bit of an extreme analogy. I do spend non-zero time working on these things... but because I was using this as a way to practice actual system admin things, they are generally set up for stability. there isn't much work to put into it after setup. Unchanged software rarely just suddenly starts breaking for no reason, especially when the traffic on it is low because there are only 2 people using the service. (again, I'm aware that self hosting email has all sorts of "you need to keep spam filter stuff up to date" weirdness, but I wouldn't advocate for that).
Other than email, anything on this list would be great for someone who wants to keep data in home, as long as they know the scope of how much free time they have vs their desired reliability.