Feels initially like a lazy thing to do but on the other side, you will empirically never have to worry about runtime errors, if Im understanding my lessons correctly.
not every function per say but for those functions which requires it, such as “api calls, handling with files, things that related to some sort of Promises that will be done in near/future, etc. and as such calls”
happy coding 
Nope. In code review you would get asked “Why does this function need to be async?”