The more I think of it, the more sense it make:
1. He has already secured Serie A top scorer award this season, and had already reached 100 goals milestone for Juventus. Individually there’s nothing more he could have achieved from playing this final game.
2. He already won trophies from domestic cup and super cup this season, playing this final league game won’t add anything to his trophy cabinet.
3. He is on the move this summer, so whether or not Juventus getting top 4 spot and plays in next season CL doesn’t concern him at all.
4. There’s Euro coming up in a month time, this could be his last chance of playing/winning another Euro, so staying fit in best condition would be his top priority now. Having played a cup final just few days ago, he needs more time to recover and ensure himself to stay free from any risk of injury.
I suspect he has already made agreement with Juventus, unless they are not winning in 2nd half and need all 3 points, he wouldn’t come on from bench.