With low interest rates, high corporate profits, and low growth, I'd expect to see a lot of debt added to balance sheets; it's a way to lever up the capital structure to the benefit of existing shareholders, as long as profits remain high and interest rates remain low. (And corporate bonds/loans are usually fixed interest, so the interest rates are locked in until they need to go back to the debt markets.)
Or you’ve already moved on, and the next CEO eats the difference. The incentives between those two vary wildly.
It’s only rational up to some level of indebtness (and often companies go too far). If you take on debt just because you can, how are you going to delever the balance sheet when earnings go down and interest rates go up?
[1] http://press.spglobal.com/2019-03-25-S-P-500-Q4-2018-Buyback...
Heavily indebted companies struggle to survive distress too.