As such, every different part of the business may request changes/enhancements - our team provides these to lots of different "business departments" across the whole company.
Again, imagine a hotel chain with hotels all over the world, each national branch may require specific changes due to local laws and regulations, or because they need to start a new incentive campaign or participate in a joint venture with a flight company or whatever.
There is one application, and N different (competing) "customers" each one considering only their own specific plans and priorities. (In case of conflicts, the pecking order will be used to solve who gets more attention: biggest hotels, or hotels in regions that bring more revenue have more "clout").
Now, when I say "we have to postpone your request for X in order to recoup 780 more days later" the guy in front of me will immediately conclude that he will not necessarily get a bigger share of these 780 days - he will have to fight for his piece just as strenuously as before, and in any case this will happen maybe in three months, and he needs his stuff yesterday - so he better insist to have his own specific request included in the release, no matter if it costs 21 days, 20 days, 5 days: he wants this to be done because the rest of his business needs it for a specific date, and everything else is just a way for IT to postpone his request once again.
In other words: everybody wants their own specific request implemented as soon as possible, and anything else has absolutely zero interest for them. Especially if it is some promise of future "gains" from guys who are constantly late.
In my experience, this is not so uncommon when you work on an app that has been developed internally (and so there is no unified marketing department which represents a single stakeholder) - note also that precisely because we have to work for a myriad different "internal customers" we tend to accumulate "technical debt" at a faster rate: there is only one codebase, and has to accommodate all these pesky requirements from all over the world...