Maybe vehicles could be disabled by shock damage and then hijacked. If you could just hijack it, then vehicles would need a rechargeable close- range shockwave like the demon walker. Or you would have to shoot the engines or something . Maybe you can only hijack vehicles from above or behind. It's just kind of a annoying to have my vehicle hijacked, but it does kind of balance vehicle vs player combat. It's still not too difficult to destroy vehicles, so hijacking is not an essential feature.

Bungie will probably throw that in, it's a legacy