It's often configurable, but e.g. carrier policy or local vendors can enforce it.
To have updates automatically install overnight is the maximally desirable scenario - waiting for user approval usually result in open vulnerabilities, and if you interact with a prompt you are by definition using your device and it is therefore a much worse time than while you're asleep.
On Android, my experience has been that new major versions are often unstable / involve some risk of bricking / include feature regressions (dumbing down of multi-task in Android 13 if I remember well). Waiting for a few month before installing a major update, while not optimal for security, is necessary to make sure that the most critical bugs are fixed beforehand.
Regarding applications, today there's so many applications being always updated all the time that there's no way it's good for the flash memory to constantly rewrite it every day. Plus this often leads to random application restarts while they are updated automatically. (and non-OSS applications updates can result in unwanted changes such as more ads, random changes in UI...).
It's still possible to disable automated updates on Android and I am glad that they allow it.
Major version upgrades are a different type of upgrade altogether. They are optional while the previous major is still maintained.
Minor upgrades is what should always be automatic.
> Flash wear
No, it doesn't matter.
Total write endurance (i.e., the number of bytes written the device is designed to handle under some standard load) is usually a large multiple of the chip size itself - say, 200x-400x, so e.g. 100TB of writes for a 256GB setup. A particular workload is only really meaningful to flash wear if it is in the scale of several full storage rewrites during the lifetime of the device.
The exact write endurance depends on the exact configuration (specific chip selection, allocated reserve), but even microSD cards have wear levelling these days.
Your device is going to die or be retired with a certain flash write wear, but I find it extremely unlikely that your device will die of a flash write wear. The wear endurance is dependent on the specific flash setup.
A much larger cause of wear is app caches (e.g., streaming video continously overwriting a disk cache, browsing social media). If you take pictures, those might end up written multiple times as first the original is written, then the automatically processed version, then any edits you make, then if storage saving measures is enabled maybe its deleted and a compressed version is written, if you later open the app the original is downloaded and written again, ...
I don't think there is such a choice on Pixel phones but I'd be happy to be proven wrong. When the next major update is available the phone just asks to update to it every few days (but won't do it without user consent). I don't think there's security updates on a given phone for old major versions when a new one is available (there likely are for older phones that don't get the major update however).
Thank you for your explanations on flash wear, makes sense. Taking a low value of 13TB endurance (64GB times 200), this is still 7GB per day for five years and I don't think app updates can consume that much.
And yes, this has actually happened to me at least twice.
I've had that happen a few times and the alarms went off on time but they used the default alarm tune instead of the one I had selected, presumably that data was still encrypted.
The amount of misinformation in this thread is huge though. I generally read every changelog for major Android updates and the amount of engineering going on is amazing. People just assumes that a few things doesn't work while they do.
Unless of course OP is using a custom alarm app this may be true, but then it is the app fault and not Android.
Edit: accordingly to ChatGPT the feature is the WorkManager: https://developer.android.com/topic/libraries/architecture/w.... I can't confirm this but looks correct to me after a quick look at its documentation.
They all even share a unified battery charging mechanism and integrated packaging for easy portability.
I'm not sure if the idea of these pocket supercomputers will ever catch on, but it sure seems like it'd be nice.
These have existed for many decades.