If you hire a plumber to fix your bathroom, and the plumber completes the work twice faster than expected, you don't get to make him do more work for free. You may hire a cheap crew, pay them by hour and direct their work, but they'll just work slowly to bill more hours. I understand that it would be nice to have a competent plumber with hourly rate, who works as fast as possible without cutting corners, but that's not the world we live in.
Sure, but they didn't hire a plumber to fix their bathroom. They hired a plumber to spend 40 hours a week maintaining all the plumbing in a building. If you discover this plumber is only spending 20 hours fixing the most pressing issues, then instead of resolving lower priority issues or backlogged maintenance they instead went across the street to handle their most pressing issues, your naturally going to be upset.
If you want to work on a per-project basis there are plenty such consulting gigs out there, but with salaried work the general understanding is you are buying a chunk of someone's time rather than specific projects.
You may hire a good plumbers to do what you're describing, but he is going to bill you for each repair separately, and will be incentivized to find as many issues as possible. That's going to be very expensive. Greedy owners would try to reduce the cost by writing a fixed monthly rate into the contract, and would cry later when the contract attracts a cheap slacker who pretends to be competent.
Many large buildings maintain full-time maintenance people on a salary basis. For your smaller general office parks these are usually generalists, but for your larger skyscrapers, data-centers, etc you absolutely can and do see electricians, plumbers, etc working on a regular salary. No they do not bill per-repair in this situation.
That's a team of cheap slackers who do just enough to keep the water running. It's against their interests to find more work for themselves. You may try to force them by adding personal liability for failures they neglected to prevent, but that's going to have the opposite effect: now only cheap and dumb slackers would sign up. The contract we're discussing is like the impossible ladder: it has many cool properties, but it can't exist in reality.
That flies in the face of my direct experience working with these people, but sure let's take your assumption at face value.
By this logic everyone on salary in any career must be a cheap, dumb slacker, after all there is no difference between accounting on salary, plumbing on salary, writing software on salary or working in a warehouse on salary. The exact same logic applies.
Or maybe, just maybe doing plumbing on salary has the exact same set of tradeoffs as doing any other job on salary and people choose either for different reasons.
Analogies are frequently weak tools because they are describing something inherently different from the primary object, and the conversation then comes to be merely about enumerating those differences. If there is a good argument to be made, it can usually be made directly, without having to resort to making an argument vicariously about something else and then having to argue why it is equivalent to the first thing in the context of the original argument.
I mean, I've hired plumbers to fix a problem, they had a 2 hour minimum charge, but it only took 30 minutes to fix the problem. So I had them do 90 minutes of other plumbing stuff that wasn't urgent (mostly hey, where does this pipe go), no additional charge.
