They used to use tiles for the heat sheild didn't they ? This foam seems to be worse than the old system of tiles.
They still use tiles for the heat shield. They are designed to handle the extremely high temperatures of re-entry. (The last project I worked on at NASA was wind-tunnel testing their ability to withstand the dynamic forces of re-entry.)
The foam provides insulation for the cryogenic (very cold) fuel tank used to get up to orbit.
Two different applications, two different materials.