Also there are law firms with the "No win, no fee" motto.
These guys are usually the worst of the lot. This type of lawyer is actually illegal in a lot of places. Why? Because the fees they charge if they do win are far, far higher than those that a normal lawyer would charge. So if they win, they take a huge proportion of the fees. They argue that they have to, by accepting other matters that they don't win on (so they don't get paid for) but in reality they almost always do personal injury, which is very open and shut. Fill in a form, send it off, get your cash. They just exploit that.
Let's look at this in a different way.
Doctor's charge per task, and they charge a sum far higher than would be received if they charged per hour.
How is charging per task any better really?
I go to the doctor or the dentist, and I know what I'm getting done, and what it will cost me. I had an hour in the dentist chair 3 days ago - 4 fillings, and it cost me $480. Was that more than if he charged per hour? Yes. But, you need to consider that I had a 30 minute appointment with him a few weeks ago, that cost me $80. So, $560 for and hour and a half, is about $310 per hour, which is about right for an experienced professional. It evens out, but it does mean they can't overcharge for tasks that they don't complete or do. Charging by the hour - you can take several extra hours and really drain all the cash you can from that file.