Lathyrus
How it works is based on the nature of how Thames Water, and other utilities are owned
Thames Water has only huge sovereign funds and very large pension schemes investing in it. There are no small or diverse share holders. You will find its investor profile in my email on page 2. You may find it enlightening.
The entities lending money to TW are its main shareholders. Now given nearly all of the owners are organisations who want income, almost more than capital growth, no tax is charged on debt interest, where it will be charged on dividends. So it is much better to get your income from debt. Debt interst also has to be paid, whether the ocmpany is profitable or not, so it is a good steady income, largely unaffected by the ups and downs of the company itself.
Obviously, if the company reaches a stage where it cannot operate profitably long term, and short term debt (to banks etc) is building up, then, of course, the debt holders are in trouble.
But in most cases this isn't the case. But generally, the aim of the kind of entities that own companies likeThames Water, like debt interest because it is a steady amount coming in every year, that they do not pay tax on - and if you are a pension fund with pensions to pay out, month on month, year on year, that has a lot to recommend it.