If I were the Raptors or the Clippers, the argument I would make to Kawhi is that if you go to the Lakers you are going to *have* to play a lot of regular season minutes, because the Lakers will have no organic depth. The Raptors and Clippers will both be in a position to sit Kawhi done for significant stretches during the regular season and still have basically a 50-win team on the court. The Lakers, not so much. They have only four starter-caliber players, no backcourt (except if you count Lebron or Kawhi as guards), no bench at all. If AD or Lebron go down for any length of time then Kawhi will be in a position of carrying the Lakers during that period, with the other remaining star.
We know Kawhi wants his minutes carefully managed during the regular season. The Raptors and Clippers can basically guarantee that, the Lakers absolutely can't. Kawhi played 60 games and averaged 34 MPG this year, AD played just 56 games and averaged 33 MPG this year, Lebron will be 35 and played just 55 games last year. There is a good chance that the Lakers will have to play dozens of games where at least one of those guys is out, anyone want to guess what the burden will be on the other star playing in those games? The Lakers can't carry Kawhi but the Raptors and Clippers can -- those are demonstrably playoff teams even without Kawhi playing.