I think someone that can carry grandma down the stairs and also occasionally put out a catastrophic fire is a pretty reasonable and efficient use of taxpayer money. The alternative would be what, having two different people to do those things?
It makes sense for them to automatically show up for some situations (eg car accidents), but there should be a properly funded triage system.
Same goes for the police, which are often called for situations where there should be some other social workers available (again, there are exceptions where police should also be present in those situations).
Which is to say the small cheaper car only makes sense after you have enough large ones and conclude you still need more cars.
That's how it is in NYC[0] too...
[0] https://www.msn.com/en-us/news/other/nyc-council-and-fdny-po...
If the two needs are distributed such that it works well to have one group of full-time workers able to do both, then I reckon that’s fine.