Same 2 who instituted it on Whitney. But I tend to agree with pack out on Shasta for a couple reasons.

1. They also have a nice composting toilet at Horse Camp (8,000 ft) run by the Sierra Club. So people have an option to camp with a toilet.

2. The other camp area is Helen Lake (10,000 ft), which is covered in snow during peak climbing season. Only a helicopter could service a toilet at Helen Lake during peak season. It's too much cost and risk to use helicopters on a regular basis. So the toilets would end up just holding waste like the old ones on Whitney that were serviced with helicopters.

Since people have a choice, and toilets would be very difficult to maintain on the upper mountain, I think the pack out system is appropriate on Shasta. But it's not a one-size-fits-all solution for everywhere. Toilets make perfect sense on Whitney. Leave it to a good engineer, sanitary workers, and a few popular llamas. The Rangers have better things to do than pick up sh!t bags and hassle people over this.