I don't. Out of my 37 batches in the past year, the past 36 have been my own recipes, not based on anything. The first was Flans Stout in the recipe database.
Also, maybe it's because we have awesome beer here that is worth replicating.
I do it from time to time as a learning experience and to help with my own recipe designs. If I can do a beer very close to one I love, I can usually figure how to tweak it a bit next time for changes that I prefer or to try a new twist on it.
That said, I only do clone recipes maybe 5% of my batches.