Is it against the law? No, and it will likely never be, because plenty of people on both sides of the aisle use it to their personal advantage. You're whining about something you have no control over, and never will.
Ah, but consider that Trump promised no lobbyists and all, yet brought people like Flynn and Mannafort in. Yes, that backs up your claim that everyone does it, but it is wrong, and was one of Trump’s bad hiring picks. These people are traitors, shame on them. You know, I served in the military myself, but I could never see trading on that knowledge and experience to a foreign government or company. Never!