It may have been possible to do an EVA... but to what purpose? Either the tiles are OK and you will have a safe re-entry or they aren't and you are going to die, either quickly attempting re-entry or slowly and painfully by asphyxiation. Why take the risk of an EVA to learn you must decide as a group how you are going to die?
I think it might be better to remain ignorant of the extent of the UNREPAIRABLE DAMAGE and not have to make that horrible choice. Perhaps, someone at NASA made it for them and elected that they not know at all of the potential for disaster. Since staying in orbit was NOT an option (no, gcochran, a resupply was not feasable in the time they had), the only possible option was to de-orbit and try to get the ship home. When all other options lead to certain disaster, you take the one that has only a slight chance of success... at least is a chance.
Had they elected to die in orbit to "save" the shuttle, I think they would have died painfully to no purpose. The altitude the shuttle was orbiting is actually NOT A STABLE ORBIT for such a large object... it is still in the atmosphere (very attenuated) and drag will eventually pull it down to burn in an uncontrolled re-entry in a very few months... probably before a salvage mission could be mounted with a new technology of tile repair that could be done in space... or a way of refueling and repowering frozen, dead shuttle and elevating its orbit.
These are just the grim realities. I am glad I didn't have to make the decision... if someone did.
They still could have collected valuable data to save someone elses' lives. BTW I suspect NASA did use 'other assests' to take pics of the tiles.