IMHO in the NFL no one other than the GM can really be trying to tank, and even the GM needs an explicit order from the owner.
If you're not the GM, and you go out there and give less than 100% as a player or coach, you might lose millions of dollars, or lose your job in the NFL entirely. Your job status and your future salary directly depend on your performance. You're not going to go out there and intentionally suck so the team can draft a better replacement for you next year. As a fan it makes sense to root for higher draft picks, but not for anyone who is a part of the continually losing team.
Even if you are the GM, you can definitely set up a team to fail but Kelce explains what the team would think of someone actively farging over the current roster of players.
The NBA is really the league for tanking. Yeah there's a lottery, but one superstar can completely overhaul your team. It's also a more top-heavy draft than the NFL and easier to predict who can adapt to the pro game.
The gentler way of tanking is when you leave a guy like Adam Gase in place all year even though you know you're moving on. No one's out there to lose, but Adam Gase trying as hard as he can is still likely to result in losses.
