I'm just sort of amazed that people felt it was worth that much apparent expense and infrastructure to have synchronized public clocks. One central clock tower with a bell would tell people what time it is.
Peter Galison's book "Einstein's Clocks, Poincaré's Maps" is based on his personal speculation that it was the late 19th C preoccupation with simultaneity that inspired the theory of relativity. Whether that's true or not, he discusses the systems in the book.
"When I came back to the United States I started poking around old Swiss, British, German, and American patents and industrial records, and it turns out that there was an enormous industry in coordinated clocks in the late 19th century. Suddenly the famous metaphor with which Einstein begins his 1905 paper began to look not so peculiar. Einstein asks us to interrogate what we mean by simultaneity. He says, imagine a train comes into a station where you are standing. If the hour hand of your watch just touches 7:00 as the train pulls in front of your nose, then you would say that the train’s arrival and your watch showing 7:00 were simultaneous. But what does it mean to say that your clock ticks 7:00 at just the moment that a train arrives at a distant station? Einstein goes on to develop a technique for saying what it would mean to coordinate clocks, and explains that this is what simultaneity is. This quasi-operational definition of simultaneity becomes the foundation of his theory and leads to his startling conclusions that simultaneity depends on frame of reference, that therefore length measurements are different in different frames of reference, and to all of the other famous and amazing results of relativity theory. Suddenly I could see that Einstein’s seemingly abstract metaphor about trains and stations was actually both entirely metaphorical and yet altogether literal. Far from being the only person worried about the meaning of simultaneity—a lighthouse keeper in splendid isolation--there was a vast industry of people worrying about what it meant to say that a train was arriving at a distant train station. And they were determining simultaneity by sending electrical signals down telegraph lines to distant stations in ways very much like the way Einstein was describing in that fateful paper."
(This is also where the NYC Times Square ball drop on New Year's Eve comes from)
Technically, you had a farther and faster reach with an optical system than you did with a church bell. But at this scale the error difference wasn't that large.
Given the noise level in the city, a bell would only cover a few blocks.
Also, this solves a different problem: having accurate clocks. Unless you want to station an attentant under each clock to reset it when the bell rings. The assumption is that there's a lot of drift in the clocks of that time so frequent re-syncs are necessary.
Mechanical clocks need regular (probably daily) winding, and drift by quite a bit per day - as much as a few minutes.
The hordes of people you'd need to employ to maintain such a system might well have been expensive enough to make an installation like this the more economical option. And, given that pocket watches were a very expensive luxury item at the time, having lots of publicly visible clocks might have been a public service that could be justified on grounds such as enabling smoother commerce.
