Your efforts are usually worth an upvote - we just don’t always have the SP to leave them.
I don’t leave upvotes after my power is below 90. I love the steemit community and the people in it - but I’m investing my time and turning it into crypto pennies. If im not making crypto pennies with my upvotes, then I just leave comments - which is like leaving my time - which I hope is seen as encouragement.