I really don't see Highway as that massive a trap card. Even if all you can do with it is to use it as a $5 Peddler, that's not THAT much more than what an actual Peddler is really worth. No, it's not a great buy, but on boards with no better $5's, or non-spammable $5's that you've already maxxed out on, it's not a terrible idea.
It's kind of like Market, which people see as a weak $5 card but which, I'm convinced, is only weak if you don't have a use for its +Buy. But sometimes you don't need its +Buy and Market is still worth picking up. Under those circumstances, Highway is just as good and often better.
The difference, I guess, is picking a Highway up when you don't have anything better to do, vs. aggressively pursuing a Highway chaining strategy. Certainly I agree that the latter only works when a real combo is available.