Bonds here just seem to me to have an asymmetric risk-reward profile.
I really can't see rates going much lower, and even if they do, the prospective cap gain you would have would not be that great because even a big move in percentage terms (say from 2% to 1%) is still a small one in absolute terms. But substantial downside risk is still there if, perhaps some years from now, rates return to their historic norms.