Humans amuse me! Particularly scientists! They have been studying why we scratch and have come up with some delightful theories - mainly that we scratch because we are stressed.
Ridiculous, of course. We scratch because we enjoy it. I love the way it makes my claws tingle, the relief when an old claw sheath falls off, the satisfaction of a good long stretch of the whole body.
It's fun, humans. We do it because we can - where we can, when we can, and how we can.
So maybe we scratch a bit more often to cheer ourselves up when we are stressed... but the basic reason is the joy of scratching.
Purrsonally I enjoy the edge of the sofa best. The furniture covering has just the right kind of tension to make my claws tingle.
And scratching on the furniture always gets my human's attention - "Gerroffit" she shouts! So satisfying.
I also scratch the doormat when she comes home. This is a courtesy greeting to say "I am so pleased you came home, look at the way I show it."
Other pleasing scratch places are the table legs in the kitchen, the door to the bedroom (when I am shut out by mistake) and of course the early morning scratch on the side of the bed to wake her up.
But best of all was the wonderful scratch I once had on an oak tree. Get your human to buy a forest.