How all scam?
Majority are, and then the numbers reach upto 99.99% we can easily say "all".
Lol you should check bounty section there have been more good bounty and you can participate.
The word "good" is relative. We dont see bounties paying out millions of dollars to every participant. While that if happening would be called a "good" bounty by any hungry bounty hunter to someone else that might not be the case. Some users are so foolish even today that handing them out some tokens of zero value and false promises is going to fetch their trust and they will endlessly shill that project. Regardless of whether the project is a failure or a scam.
Legal or scam bounty it will depend on your own research so be careful when you wanna participate a bounty, like should follow project activity, IEO, Exchange, products, team profiles, and very impressed their partnership.
Nobody does that though. Majority of the hunters here are from low income countries and they dont bother to check the "Scam Accusations" section of this forum. Neither they do they want to learn how to detect scams.
Also the point what I said in the first line, it ends up being a goose chase so they hunters try their luck on every bounty essentially spamming all of them and getting zero worthy tokens in return or worse, none at all.