The role of tire pressures, and especially for the front tire, has grown in importance in recent years, as aerodynamics and ride-height devices have made the front ever more sensitive to pressure and temperature changes. It is common to hear riders complain of temperatures and pressures skyrocketing after getting stuck behind other bikes, and kept out of the cooling air.
It is therefore not surprising that factories and teams try to manage tire pressures as carefully as possible. By lowering the pressure, they can keep tire temperatures lower and allow the riders to better manage the front tires over the duration of the race.
They have to be careful not to go too low with tire pressures, however: like all motorsports series with a spec tire, MotoGP has a minimum pressure for both front and rear tires: 1.9 bar front, 1.7 bar rear. Tire pressures are monitored by sensors and recorded by the spec datalogger, and pressures have to be over the minimum for at least half of the race.
Bending the rules