In Ron Howard's Backdraft, two firemen run for their lives along a rooftop as fire explodes, causing the building to cave in. It was clearly only going to be accomplished as a visual effect. ILM brought the spectacular fire scenes to life. Computer effects are not the only thing that ILM handles. ILM also has a staff of model makers.
Films require detailed models to give the effect of real objects.
The Empire Strikes Back, and Rocketeer. ILM is still setting new and higher standards in movie making, and without the influence of Lucas, the effects of today would not be possible. Many say that school is not supposed to be fun. School is for learning. Lucas is not one of these people.