Concurrent sentencing was the norm back in the UK. I think this was because of a quirk in English law regarding multiple crimes in one incident. If the top sentence in a consecutive list went away at appeal, so did all the others. Weird, huh? Maybe some states here have there laws written in a similar way.
A lot of concurrent sentencing involves exactly this - multiple crimes in a single incident. The goals of sentencing are much broader that just deterrence or punishment. Courts are also required to consider rehabilitation, remorse, cost, etc. Oftentimes it seems there is little purpose to be served in sentencing someone to what might amount to a life sentence over a single incident, especially if it is a non-violent incident and they do not have a significant criminal record. Or you might see it in, for example, a sentence for aggravated assault where someone pointed a gun at the victim but no shots were fired and no one was injured. As opposed to an aggravated assault where someone actually got shot or maybe multiple people got shot. Same crime, different facts. The facts matter, even where the charges are the same, and all of the factors above have to be taken into account. This is the type of situation where you see the majority of concurrent sentencing.
Another factor is expense. Frankly, it costs a lot to keep people in prison. I used to have lots of people tell me to "throw the book at 'em!" OK, fine, do you want to pay for that? For a few thousand people? Would you like to use the money scheduled to build schools used instead to build prisons? We can't hire enough guards in Wyoming now. Imagine how much worse it would be with a couple thousand more inmates.
In the more violent crimes that truly deserve long sentences, consecutive sentences are often used to insure just that. The formulas used by corrections departments to reduce time served for good behavior are too much to explain here but, at least in Wyoming, a ten year sentence might actually get only about 6 years actually in jail. The courts have no authority over those rules. So if I thought someone needed to be there longer, I would stack up a few lengthy terms to be served consecutively. That is, you don't start serving #2 until you've finished #1 and so on. You could run up a lot of years pretty quickly that way.
It's a complicated question that tends to be very specific to individual cases, way too much to try to get into in detail here, but maybe this will at least give you an idea as to the thinking that goes into the question.