does stainless steel catch lightning strike?
As others have stated hardwired smoke detectors (usually with battery backup) are required by code in most places. In addition they are usually interconnected so if one goes off, they all go off. That way if you have a big house and/or are a heavy sleeper the alarm closest to you will still go off even if there isn't any smoke there yet.
Go to your ironmongery shop and ask for PL premium. This glue is the strongest ever and very durable. It is available in a tube and you can desire a caulking gun. Its now not clear glue but when put sufficient on the within where its cracked and stick it on the cup and wipe the excess off, you won't even know it was once broken.
I think it may be common in new houses with integrated security and data lines. The problem I have with it is hard-wired detectors can fail like battery powered detectors. Replacing a battery powered detector is easier than finding a replacement for a hard-wired detector.
Here in the US, it is code to have hard wired detectors with a battery back-up. Very common.
Smoke detectors are required by NEC code to be hard wired with battery back up in new homes.
