Because the trade off isn’t worth it.
While it’s nice having extra sunshine in the morning or evening depending on the time of year, it is quite disruptive, especially with kids and working with teams across timezones etc.
But more importantly, people actually die from it. Consistently, and predictably. I can’t in good conscience support a policy which is merely “nice” for me but will literally cause other people to die.
Do you have a reference for Signal using SGX for keys?
Everything I could find was about metadata and private data, e.g. contact lists (which is what the SVR thing that you mention is), but nothing about keys.