Many bus routes have a 5-10ish min break at some point (usually the main station) in the route. If you can utilize those ten minutes to do a top-up, you can go a lot further on the same sized battery.
In short there are plenty of places to switch buses if you need to.
People through history have always considered about half an hour a reasonable daily commute. Doesn't matter if it is a hunter-gatherer going to their gathering grounds (if they follow herds they will move camp if the herd moves more than half an hour), or "modern man" going to the office, half an hour is what you get. Everything I said is based on making as many of those half hour trips possible as I can - but not all trips can be done that way and some locations will be left out.
Not only is that slower, having the first bus stop there and turn around instead of going all the way to B hasn't benefited anyone else either. The route from the first depot to the halfway point is still being covered by the same bus route. The interval is determined by how many buses cover that route and not just by its total length, and another bus that covers that section of the route might even go somewhere other than B after reaching the point you'd have had it turn around to go back, also giving a faster option than multiple transfers for people who want to go from A to C. When A, B and C are all high density areas, creating direct routes between them makes sense even if they're each more than 15 minutes apart.
This isn’t how bus routes work, and this isn’t how people ride busses, on most if not all of the…many PT systems I’ve used in multiple states / countries.
Imagine a metro area with somewhat grid-like streets (or at least common paths) that go on for an hour+ in each direction. People still generally cluster to 20-30min from the destinations they care to go to, so it doesn't break that standard. Breaking it up into four 15-minute stretches isn't making it better for anyone. All you're doing is forcing people to get off one bus at an edge and hop on another. Just run more busses on the full path so there's still ample service for the changes.
How does forcing the 15-minute max path make more destinations available?
You could also just have more lines even if they're long. The length of the lines doesn't change the number of them. It's just a question of how many busses and drivers do you really have and what service interval are you trying to hit.
If you're arguing they should have like a 15 minute hub and spoke model, you might also be forcing some really inefficient routes and once again force people to change busses more when one bus route could have better served the community.
The other aspect is the what city topology you are dealing with. In square grid cities, you can probably put a tram on every road, and with one switch over, get to where ever you need to get to.
But many organically grown cities end up using the hub-and-spoke model, where there are main stations where many different buses meet. People switch over to the next connection (and you need a buffer here). Critically, you need all the buses to meet at roughly the same clock time, say every 30 min. Now, one thing you realize immediately is that not all routes are equal. One route might be only 25 min, Either you make it longer and waste fuel, and time for everyone sitting on the bus, or you wait an extra 5 min at the main station.
Bus scheduling is very difficult problem in real cities with weird topologies and real traffic issues. Buffers are a necessary part of any reasonable solution.
(1) Better scheduling system. My opinion is that most real world systems are not too far away from the optimal trade-off curves. There is always room for improvements, or choosing better trade-offs, but it will rarely drastically improve things.
(2) More ridership: Most problems with speed just disappear if more people ride. For example, you do need a solid buffer when buses come every 30 min or more. But buses that come every 10 min or less, you can get rid of all buffer. A lot of scheduling problems are just not-enough-users problem.
Every workday I take a one-seat King County Metro bus ride that lasts about 1 hr. The bus starts at a layover facility and ends at a different layover facility.
I don’t see how this 15 minute interval maps to my actual commute?