I trek regularly in Nepal and a couple of Sherpas are good friends of mine. One has just summited for the 9th time.
There are different types of Sherpas - it's a race/culture, not a job. If you're looking at the jobs they do, there are porter Sherpas, cooking Sherpas, laundry Sherpas, guiding Sherpas, and the most important ones - climbing Sherpas. Each one of them will be paid for their job.
The lucky ones are the ones who get to work with the western climbing teams - Jagged Globe, RMI, etc. because they provide all their Sherpas with the appropriate kit and insurance. As a client, you get the best of both worlds - western organisation and risk assessment, and Sherpa climbing knowledge. The worst outfits are the Nepalese ones - they take large groups up, and don't interview them re their climbing experience. A successful summit of Aconcagua isn't going to be enough for a Western team to let you up with them. Someone like Seven Summits (Nepalese) won't check this, and so when you get up there and have trouble, you'll probably die.
The Nepalese outfits take too many inexperienced climbers up, with a large client/Sherpa ratio. They leave their rubbish, and don't insure properly. The western outfits are the ones who take care of the mountain.
Also - it's all very well bringing your rubbish down from the mountain, but there is nowhere to put it in Nepal - they don't have any kind of recycling or waste disposal infrastructure. The whole "what to do with rubbish" question is far too big for mountaineers to answer - it's a massive international development question. The only way to get rid of it when you're out there is to bring it all the way home.