A typical project involves several people, and while the number of people who travel to Hawaii for a given night varies widely from project to project, the average is 2 to 3 people. This means substantial sums are spent by the member institutions on travel and related expenses. In addition to these operational advantages, there are strong scientific advantages to remote observing as well. With remote observing, every member of a large collaboration can participate in obtaining the data. The inclusion of students in the observing session becomes much easier and more routine when no travel is required, they don't need to miss classes, etc.
Astronomical images are large.
The optical instruments currently in use at the Keck Telescope have frames that are 8 megabytes in size, and soon these arrays will become 3 times larger. Integration times depend on the scientific program, and range from less than a second to an hour. The quality of ground based optical and infrared astronomy observations is very sensitive to weather conditions, including clouds and atmospheric turbulence. Remote diagnosis of problems becomes feasible once a high speed network exists. The teams that built the instruments for the Keck Telescope are located at Caltech or a campus of the University of California.