It is a truism in MotoGP that though they hand out the trophies on Sunday, the race is often won on Friday and Saturday. Practice is when riders and teams can find the setup tweaks they need to go faster, evaluate tire choices, and plan a strategy. Which tires offer the most potential? Which area of the track can we gain most while sacrificing the least in other points? Is there more to be gained by pushing hard early and trying to manage, or by being patient in the first half of the race, hoping to have an advantage in the second half?
The wide range of tires offered by Michelin make practice even more important. Michelin's remit from Dorna is to produce three front tires and three rear tires that can all be used during the race. That requires a certain amount of compromise: labeling tires soft, medium, and hard does not mean that Michelin make three tires with an equal step in between the three different tires. It is more like an indicator of how well the French tire make expects each tire to cope with the heat and stress of a race, and the trade off in terms of grip. So a soft and a medium tire may use the same rubber on one side of the tire, or on opposite sides of the tire. Or they may use the same compounds with a stiffer carcass, to reduce flex and therefore the amount of heat being generated.
Understanding how all these factors work together, and what that will mean for the race, is what the teams spend their time doing in practice. The team and rider that does this best on Friday and Saturday gets to spend Sunday evening celebrating their victory during the race. If all goes to plan, of course.