Even though we have disagreed a bit here, I have to step in for these hay farmers...
Hay farming fills a huge agricultural requirement for our country. As stated, a large portion of livestock farmers, whether it be for livestock or even those with horses for recreation, depend on hay farming because they either lack the ground to raise their own feed or prevents the purchasing of their own equipment.
Hay farming is a great second or alternative income for small farmers or property owners. Many hay farmers I know work full time jobs and making hay provides them some extra money along with a way to retain land they own rather then have to sell it out. Some parts of the country, much like Noble county, OH where I live is very poor crop ground, but it is great hay ground.
And as crop growing agricultural practices go, hay is one of the most environmental. Do hay farmers have to use artificial fertilizers in a lot of cases, yes, but it is too costly to over do it. Very little, if any, pesticides are used to grow hay.
A hay field is not tilled, therefore retaining the stored carbon. In comparable biomass terms, grass sequesters 6x more carbon than trees do. Ground used to produce hay contains exponentially more biodiversity in the forms of microbes, fungi, invertebrates and plants.
Not to mention a hay farmer has to own and maintain FARMING equipment. They are farmers.