There is no obligation but pretty much standard practice around the league is that team's engage with their star players at this very time during their rookie deals. And there are very good reasons why this is done. Few teams, if any, make their star players play out there contracts and then sign them to a large extension. It's just not how it's done.
And yeah, the criticism of Lamb is dumb. He was a top 3 WR all of last year and a lot went wrong in that first half. Potentially pissing him off with a contract squabble because of like small incident during a game you were getting DESTROYED IN is stupid and dumb. But Jerry has never been one to handle these things correctly.
Every year the same group of fans whine about pampered players and we shouldn't pay them now and they should honor their contracts and this and that when the reality is the league doesn't operate that way and if you try to operate that way, it often just ends up burning you.