Unless players see a #1 or #2 pick that is going to take their place on the roster.
"Hey, go win the game so we can pick up a new starting point guard and kick you to the curb."
If you are so worried about your roster spot being up-for-grabs because of an incoming rookie, then you are probably not going to be long for the NBA. A new draft pick is not likely to kick an established starter (even on a bad team) out of the NBA. He would more likely kick off the last guy on the bench barely holding on.
Plus, as guys like Harrison Barnes show, modestly okay or even mediocre players on good teams can often use that perception to cash in elsewhere. Everybody wants to hire the "winners" away from the good teams, even if the role players on many winning teams are nothing special and are carried by the important superstars.
Was Barnes really worth what Sacramento gave him? Or was it just easy to play alongside Steph and Klay?
If I'm a starter on a playoff bubble team who could win that postseason tournament for the #1 pick, then I want that kid coming to join us because he might make the team look better and me by extension.