Firstly, it's the lack of evangelism. That I have said many times before. So I won't even consider that as the common sadness, it's the root cause of the common sadness, which is the lack of true Christian Fellowship. At least this part of town (East Coast), among the Reformed influenced churches that I've been.
Erroneously equating friendships (or worse - 人情 - hospitable kindness), collegial relationship, with fellowship (or even with Gospel). Falsely assuming that Christian fellowship is only for Sundays in churches.
Christian Fellowship is suppose to be closer than immediate familial ties! Matthew 12:48-50