Braiding the mane use to be restricted to English horse shows where the mane was braided into small tight rosettes. Nowadays braided manes are showing up in western disciplines.
Lattice work braids (shown below) are very easy to do and less time consuming than braiding those tiny little English rosettes. They are the style that is showing up in western classes.
Back in the days when I use to actively show my horses, I use to know several people that would make money as horse mane braiders. They would either charge by the hour or by the mane and the type of braid to be done. They told me that they could easily make several hundred dollars on the morning of a horse show.
Braided tails are not as elaborate as manes can be. Most of them use a simple french braid around the top 1/3 of the tail. The only horses that I have ever seen with a completely encased braided tail are polo ponies.
Braiding manes and tails is not only an art form but also hard on your fingers and hands. It also takes someone with a good eye to make a mane show off the neck and overall appearance of a horse with the use of braids. While a good braid job will enhance the look of a horse for a show, a bad braid job will just the opposite – and I have seen plenty of bad braid jobs.