Motorcycle racing would be a good deal less complicated if it was an indoor sport. Leaving the complications of housing an area covering several square kilometers to one side for a moment, having a track which was not subject to rain, wind or shine would make things a lot more predictable.
No longer would the riders and teams have to worry about whether the track was wet enough for rain tires, or slicks could be used with a dry line forming. Nor would they have to worry about track grip dropping as temperatures rose beyond a certain point.
Or differences in grip from one part of the track to the next, as clouds hide the sun and strong winds steal heat from the asphalt. There would be only the bike, the rider, and the track.