On an accounting sheet I can see my interest rate and how much I'm paying monthly and make decisions. With technical debt, it's all about people time, and people time is a sunk cost to your finance department.
With tech debt, you can ask several engineers and get very different answers about how much tech debt there is on a particular project. It's not well defined, subject to interpretation, and so doesn't fit well with management wanting quantify the objective value of doing something. I think this is the real reason it's often disregarded.
It requires a degree of trust from management to the engineers to properly address, and that trust can be abused. All sides are aware of this and I'm sure I'm not the only one that has used tech debt as an excuse for some minor padding here and there.