Obi-Wan Kenobi failing to use the Force

When I first watched "Attack of the Clones" and "Revenge of the Sith", I thought that there are a number of situations where Obi-Wan Kenobi makes life difficult for himself by failing to use the Force (we'll excuse him in "Phantom Menace", since he is still an apprentice). Two that come to mind right now are:

• Fight against Jango Fett on Kamino. He just uses his lightsaber to deflect Fett's blaster shots, instead of using the Force to fling the blaster of Fett's hand, or straight up throwing him against a wall until he's knocked unconscious.


• Fight against Gen. Grievous after both have lost their lightsabers. Five minutes earlier, OWK had shown he has enough Force command to fling Grievous around a huge hangar like a doll, but now he insists on trying to punch an opponent made of metal with his bare hands.

Is there an in-universe reason for these decisions?