Since everyone forgot about Thunderstrike and they don't care to use him again because Thor is back. That's why he existed in the first place. To replace Thor while he was gone. They don't need two Thor's ...asshats..
Plus he died in such a heroic manner, it would take away from that if he was brought back. I would love it...but he should stay resting in peace They tried to use his son in a future type thing