Its obviously a questions of economics.
It would be awesome if an interventional cardiologist turned up outside your house in a giant flying cath lab for every chest pain call. But there are a few issues with that.
Obviously a doctor on an can do more than a paramedic but I think the question of "How much more?" and "To what effect?" are reasonable questions to ask when presented with the bill for replacing our 2500 paramedics with doctors. I realise that's not really being suggested, but I'm just extending the idea a little for the purposes of discussion.
I think its reasonable to suggest that given the limitations placed on us by time, equipment and a highly risk adverse society, a doctor's extensive training is a little superfluous in most areas of ambulance.
That said, a paramedic's training, especially in America is woefully inadequate to meet the demands of the future (and quite probably, the present).
To provide a different perspective, paramedics here are more educated than they need be in some ways and less educated in many others. By virtue of how our university entry system works, the popularity of the degree and the courses before it going back probably almost 20 years, you get quite a few high achievers becoming paramedics. You then however, get an education system that is apologetic for teaching you anything other than guidelines or "need to know" facts, because our system is essentially designed to protect the lowest common denominator by restricting practice. As such, the high achievers skill atrophies or they never really bother developing them in the first place. You have a system full of people capable of much broader scope (if only the programs were put in place to allow it) held back by a few idiots. There are of course economic and administrative issues that complicate matters to no end, but there you go.