And since you're trading unguaranteed money (future seasons' salary) for spread-out guaranteed money (prorated bonuses), you can't cut or trade that player without getting an anvil dropped on your salary-cap plans. So if you "cook the books" or "kick the can" or whatever metaphor (It's easy! Any team can do it!), you're hoping that this is a dude who can play the whole term of his contract, who won't change for the worse when a huge bonus is dropped in his lap, and who won't be a big cloud of stink in the lockerroom.
My local team, the Saints, had their head coach leave for the Rockies once he saw that his retirement-postponing QB wasn't postponing it anymore and years of his prorated salaries were gonna come due -- causing them to cut more players to clear cap space. Now that I write it out, I'm thrilled he's got a Russel Wilson-sized hole in the 2023 and 2024 salary caps.
Personally, I don't subscribe to the "If we spend a lot of money and make it to the Conference Championship, I'll be okay as the division's doormat for seasons to come!" THAT is what I think of as true credit-card mentality.