I think people suggesting "build it from scratch" mean build a local Uber-like service from scratch, which like Uber would not own vehicles itself or pay for gas or maintenance. That gets rid of the buying vehicles, and covering gas, maintenance, and tires.
Dispatching drivers could be done with pairs of text messages to the driver, of the form "pick up <NAME> at <ADDRESS>" and "drop off <NAME> at <ADDRESS>". The driver can tap on the addresses in those text messages to open them in the driver's smartphone's map application. That gets rid of the need for a commercial map license.
I don't see any need for a payment back end. The town can require drivers to accept payments directly using one or more specified methods (such as Square).
It probably doesn't need native iOS and Android apps. A web-based application should be sufficient.
They already have a website. They should be able to add the back end stuff to that, so no new costs for ops or hosting. (That is assuming that they have access to the code for their site and can make changes. Their site is run by Pathfive.ca, which seems to be a company that specializes in building and hosting websites for educational institutions and local governments. It may be that the town only supplies content to fill in templates).
Why hasn't anybody executed on that strategy (in practice)?
Forget the government affiliation, someone could be minting money either by competing with Uber on cost or just strategically choosing smaller markets that are not yet covered by Uber.
Why aren't they?
For comparison, in an average German town, a bus costs annually $80'000, including maintenance and driver. From scratch or rented from a company offering bus services.
a typical California city must contribute quite a significant sum so that the bus driver can retire at, say, 70% of their highest salary level. (e.g. over the past year, about 20% of Los Angeles's budget went to paying for the retirement of past employees.)
how does Germany do it?
The rest is handled by the employee.
Pensions are paid by the employees pension insurance, and the federal pension insurance, not by the employer.
There was a distant time where some bus drivers were also appointed Beamte but that practice was done away decades ago, so there are only very few such drivers left.
So what are the most successful examples of non flashy websites running on cheap hosting you'd recommend?
But now you're saying they should buy vehicles, hire drivers, hire an iOS dev, an Android dev, a back-end coder, an ops team to watch the servers 24/7, a coder to handle payment back-end, a general manager to run the whole thing, pay AWS or GCP or a bare metal hoster for the servers, hire customer support to handle issues, pay Google (or Bing) maps commercial license fee, cover gas, maintenance, tires for all of the aforementioned vehicles and still have a lot of money left over from that fat $610,000 check to justify this project?