They don't have to make any decisions on a large percentage of the remaining deliveries (besides calling no-balls which they haven't been doing).
This is actually very wrong, especially when you're umpiring at the highest levels, but a very common misconception people have about what umpires do on the field.
Because you'll probably ask me to elaborate, and because I like revising this stuff:
Let's leave out deciding on wides, no balls (of all sorts) and dismissals. I assume you know the umpire has to do all of this. The rest of the stuff that the umpires (on field and third umpire) are responsible for each ball and each over is:
- Ensuring the fielding regulations aren't being violated. Especially important in LO cricket. This involves following the movements of the players across the field in between deliveries and even as the ball is being delivered.
- Following the movement of batsmen, bowlers and fielders across the playing surface (there are laws and PCs in place for damaging the turf).
- Following the movement of the ball across the field (keep an eye for tampering, ensure the condition of the ball is satisfactory, and watching out for those cases where the ball hasn't gone dead but some players may think it has).
- When the keeper is up and/or fielders are around the bat, you're responsible for ensuring there is no encroaching on to the stumps and playing surface (laws and PCs in place regarding this)
- Keeping an eye out for other violations of fair/unfair play (in practice you're mostly looking for fake fielding and distractions)
- Constantly evaluating if conditions are fit for play (see the sunlight issue in today's NZ vs India game)
- Ensuring the spirit of the game is upheld (basically dealing with players being ****s to each other)
- Keeping track of overrates and general timekeeping (which gets difficult when you have repeated interruptions in play)
- Keeping track of the score (umpires often need to correct scorers, and need to have good communication with them to ensure every signal they make is picked up and noted down. This is mostly done by the reserve/third umpire)
- Keeping track of injuries, substitutes fielders, player going and coming off the field
And this is just the extent that I know of, and i'm just a rookie umpire. I'm sure a professional could come down here and list out another dozen things that I have missed out on this list. Give me a few hours and I'll probably remember a couple more.
There are, of course, lulls in play where things go smoothly and you're kinda on autopilot. Saying they have to work on each and every of the 600 deliveries in an ODI is clearly an exaggeration. But they are making decisions and working during a large percentage of deliveries in a game, contrary to what you think. An umpire has to be the first person in the ground to spot any violation of any of the laws/PCs, and has to be in position to deal with it correctly in a timely manner. We all expect that of an umpire. In order to deliver that, they are hyper vigilant and basically trying to catch something that happens before it happens. We even have subtle little tricks we do once we see a potential problem forming that we aren't allowed to explicitly warn a side about, in order to stop it before it actually happens, so that we don't have to deal with the fallout once it does. And wherever we are allowed to warn players, we do so, and we are very keen about doing so.
And this is just while the game is live btw. We're not even touching the work they do in between session, or before and at the end of play
Sure all jobs are thankless. But no one is sitting around on a forum criticizing Daemon on his accounting ability whilst having next to no knowledge of what accounting entails, and without realising the extent of what Daemon's job is. That's why the ICC are the ones who decide who a good umpire is and who isn't, and it's not left to the court of public opinion. I say thankless, you say scrutiny. I think we agree on the general point here.
And they do make good money, that's true. Well deserved IMO.