There are three types of legal work (exceptions, yada yada, but mostly):
1. Normal people shit. Parking tickets and most criminal law, etc. Flat fees fine and usually nice so your clients understand (and understand their ability to actually pay your rate). Work itself can be pretty predictable, or taken on contingency for civil stuff.
2. Line of business legal work. If you fuck this up it sucks, but rarely is it a material risk to the value of the company. This work is usually brought in-house ASAP, to control costs. Before that point, you see both hourly and flat fee work, mostly based on client sophistication to negotiate such things.
3. Bet-the-company (and white collar/wealthy criminal) work. Here clients only care about one thing: WINNING. You win M/A by closing. You win regulatory work by clearing the way for profit making activity. You win bet the company litigation by....winning. The cost of legal services, even at hourly rates, are negligible compared to the profit making ability success unlocks (or unlocks the continued existence of the company, a guy not going to prison). Clients rarely give a shit what or how you charge as long as you win. They will pay whatever "winners" charge. They will only bitch about costs if they percieve themselves to not be winning.
You cant talk about this as if legal work is the same. That's probably why you percieve a disconnect as an outsider.