Any job where there is not much recognition or you are taken for granted can seem like a thankless job. Author Ruth Harms Calkin stated it well:

You know, Lord, how I serve You
With great emotional fervor
In the limelight.
You know how eagerly I speak for You
At a women's club;
You know how I effervesce when I promote
A fellowship group.
You know my genuine enthusiasm
At a Bible study.

But how would I react, I wonder
If You pointed to a basin of water
And asked me to wash the callused feet
Of a bent and wrinkled old woman
Day after day
Month after month,
In a room where nobody saw
And nobody knew?

We know what she's talking about, don't we? Thankless jobs. Jobs without much of a payoff in money or recognition. Repetitive jobs, boring jobs, repulsive jobs.

Being a shepherd is a thankless job. It really is. Imagine dealing with dumb, smelly sheep all day. In Palestine, flocks of sheep are plentiful. They dot the countryside, clutter up highways, crowd the streets of towns and villages. The shepherd with his long staff walks in front of his flock and his sheep follow him. In fact, they crowd around so closely they hamper the shepherd's movement. Dumb, helpless sheep.