"So what exactly is wrong with phosphates? Why don't they want us to have them?"
Phosphates got a bad rap in the 1960's and 1970's as one of the primary cause of alage blooms in bodies of water. Phosphates are very good food for plants, and the excess growth of plants in any body of water robs it of oxygen, thus all living creatures who need said oxygen die.
Soooooooo long story short, states began to ban phosphates for domestic laundry detergents. Commercial laundry and automatic dishwasher detergents got a pass. This was because they were able to lobby that no other chemical was effective and it was a matter of sanitary laundry/dishes.
The Clean Water Act gives the federal government some ability to control local water supplies in that sewage and drinking water must meet certian standards. Ironically a bulk of phosphates used are for food processing (mainly processed meats), and fertilzer. Golf course,lawn, and garden run off probably contains more phosphates than laundry detergent water ever did. So does human waste (by products of human digestion and all the phosphates used in processed foods). Thus the Feds can and do make local water treatment plants filter out phosphates. So it behooves states and local areas to control phosphates as much as they can. NYS used to allow commercial detergents with STPP, but that now is off.
L.