Again, they don't have to bring it back - it was going to be taxed regardless. They could pay the tax and invest it somewhere else. They chose to invest it here.
Analogy: Anyone can open a cryptocurrency masternode [1] and get a several percent per month ROI, paid in that currency. I don't want to do that unless I believe in a given coin, however, because I must invest in and hold a large amount of the given coin in order to operate the masternode and get the return. Yes, I am being incentivized to do so, but it still doesn't make sense unless I believe in the underlying investment.
[1] https://masternodes.online/