In support of your point, and to help clarify it, there’s a lot of train lines where the cost (and the carbon output) of electrification is far beyond the benefit. A lot of the North Wales coast, for example, because working in the tunnels would be prohibitively expensive. In these cases it makes sense to have bi/trimodal trains, at least until electrification technology makes significant breakthroughs.

Another example might be cases where an old rail line (e.g. ex-mining) is looking at being reopened at a low capacity. It would be madness to immediately electrify. An example I have looked at was running a train for tourists on what is currently a little-used freight line (that still uses tokens!) in the Lake District.