Why are major telecoms companies asking Accenture for help? Do they not have their own devs? If Accenture employees are this bad you might as well hire anyone with software engineer on their CV.
Having to hire in more staff creates cost liabilities for them. They'd rather outsource things. That means they lose the skills in-house, and often end up needing consultants to help fill the gaps in their knowledge (after having lost their skilled people to the outsourcing companies, or other sectors).
Some telecoms companies have outsourced their development to Tech Mahindra and others already... And yes, in my personal view, they'd be far better hiring random software engineers and undoing the decline in control and understanding of their own business they've overseen.
I've seen car dealers offering significant discounts because they are trying to hit their end-of-quarter target. I've locked-in phone contracts with service at below the actual handset cost (when multiplied out by the contract duration) because I called late in the day on the last day of the quarter, and staff are trying to hit bonuses.
Something you do see a lot in telecoms is entering an outsourcing contract where you transfer your own (skilled, experienced) engineering staff out to the contractor - this is long-term suicide, but in the short-term it reduces your outgoings on the balance sheet.
To me, this is proof that it's just a game of short-term balance-sheet bingo, and I think you hit the nail on the head - the managers won't have to deal with this, as they'll bounce to another "generic business role" and ruin that organisation in a few months.
Here's an eye-opening post: https://berthub.eu/articles/posts/5g-elephant-in-the-room/
Youd think banks would be tech companies but they dont have a good rep for being a dev there in most cases