A lot of people in the horse industry have probably at some point envisioned themselves mounted upon a great horse with a long flowing mane and tail. Some of us still aim and hope for that for our current horses. A few of us consider that long, thick, flowing tail a blessing, others might think of it as a curse instead.
For many of us, the tail just adds to the overall picture and makes the horse look 'complete' or otherwise astheticly 'balanced'. I know one of my own mares has a tail, that at the moment resembles something you may find on an elephant- stick like with fringe at the very end. It is not "appealing" nor does it "complete" or in any way compliment the overall picture she presents.
Manes and tails are to some degree a product of the horses genetics. I have seen and dealt with wispy tails on a number of horses from the same sire, dam or combination of the two. Their resulting foals don't seem to stand a chance in this category and they are forever resigned to a life with a thin, wispy mane and tail. Appaloosa's generally didn't have much to speak of in the way of manes and tails. Some of them were blessed and for the most part- the rest were not. I have also dealt with thick full manes and tails, which were passed on for generations in various breeds.
Within the Saddlebred and Tennesee Walking Horse circles, tail setting harnesses are quite common in the show barns. (The one pictured is $399 from World Champion Horse Equipment.) To many of their enthusiasts, a tail comes out of the horses haunches high and flows streamingly out behind them. I have seen tail setting harnesses on Hackney ponies and a few Shetlands as well. It seems they too are striving for that same look. Arabian horse folks seem to agree and like that look, but haven't yet gone as far as the tail sets and harnesses to attain it. At least not that I am aware of.
When you shift your focus to the draft breeds, you'll find some of the owners and breeders prefer to dock the tail. It keeps it from becoming entangled in the harness and causing problems while they are working in the field. Others choose to braid it up instead. Docking the tail leaves the horse without one of their natural defenses against flies.
On the market there are a number of items you can purchase in hopes of growing, protecting, enhancing or otherwise caring for your horses tail. Some of them work to a varying degree, others are a waste of time, money and hope. Shampoo's, conditioners, sprays, lotions, ointments, gels, leave in, rinse out- the list is long and the price may vary, but it can be shocking the amount people will spend to get a look for their horse to have what they have deemed a "pretty" tail.
**Don't worry, I will be addressing gingering, tail bags/wraps and fake tails in their own discussions. I feel they each deserve their own attention. **