I'm going to show an opposing viewpoint here: I believe this is the thought pattern that screws developers over.
It's not about being sociopathic. You said it yourself: it's just business. Really, that's what it is. You are exchanging skills for money, if one party isn't happy with the agreement, they can terminate it. Don't confuse the issue with wording like "hang them out to dry" or "professionalism." Professionalism has nothing to do with martyring yourself. If you're unhappy with anything enough to leave, then leave.
I agree with what you're saying, but that isn't what we're talking about here. We're talking about the idea of it being unethical to shop yourself around with no intention of accepting a competing company's offer. I see this as ethically neutral with respect to your current employer, but as kinda unethical with respect to the other companies whose time, effort, and resources you are wasting by pushing yourself through a hiring pipeline with no intention of following through.
If you can get a better deal from your current employer via other means, you should certainly do so. If not... well, I'm personally uncomfortable interviewing at other companies with no intention of accepting an offer. Opinions differ, of course.
It's not about being sociopathic. You said it yourself: it's just business. Really, that's what it is. You are exchanging skills for money, if one party isn't happy with the agreement, they can terminate it. Don't confuse the issue with wording like "hang them out to dry" or "professionalism." Professionalism has nothing to do with martyring yourself. If you're unhappy with anything enough to leave, then leave.