I often hear people mention the bat made out of English Willow. Why are certain types of trees prefered?
One reason for this is, it is a tradition and is the ideal wood for this. Normally all the cricket bats are made of english willow and they are still following that tradition.
As per Wiki the other reason is, it is very tough and shock-resistant, not being significantly dented nor splintering on the impact of a cricket ball at high speed, while also being light in weight.
In 1979, Australian cricketer Dennis Lillee used an ComBat aluminium metal bat, but after getting the complaints from English team, Australian captain Greg Chappell asked him to revert to the wooden bat. Later Kookaburra released another type of bat that had a Carbon fiber-reinforced polymer but that was also banned by ICC.