Not a card you would think of as being very notable, but ends up being useful in a lot of decks. You never actually build around the mount trait unless using Elfhelm, but often have a couple in your deck that play a key role - think Armored Destrier + Beregond, Asfaloth + Glorfindel etc. Because they're usually unique and/or restricted, and many of them are meant for specific heroes, running three-ofs isn't very palatable either. Westfold Horse-Breeder is a good, noncommittal way to boost your chances of finding that mount, assuming you have access to the blue moneydollars. It also acts as a deck thinner if it hits. A one-for-one willpower ally/chump isn't bad anyway, so it's not a big deal if you miss. Also benefits from some powerful Rohan effects (Théoden, Ride to Ruin, Helm! Helm!...)
In short, consider using if you have a hero and a high-impact mount.