I have a couple of them I have tried to introduce steemit to. The excuses are mostly the same - 'I can't write', 'internet is full of Ponzi scheme and scams', 'I don't have much time'(they are always on facebook and others).
The best thing to do for these people is to succeed and show them your results. Any doubting Thomas or lazy people that still refuses to join after seeing your success is beyond redemption.
You have said it all already @golddeejay, all we cannot force anybody to join if they don't want to join.