I think it amounts to personal preference. There seems very few impartial studies and from memory the ones that I was able to find (a while ago now, not sure about recent studies) weren't all that comprehensive and didn't really indicate a benefit. There are all sorts of claims that amount to "The Ponds Institute" type of science (where "scientific studies" show that our wrinkle cream reduces the visible signs of aging) lol.
So to me, they are a waste of money. They make your car run better while it's in the tank (raise the cetane rating, possibly giving a slight increase in efficiency?) but that's about it. No lasting benefits I am aware of. I find things like the "diesel purge" and associated claims very dubious also.
At any rate I have had plenty of cars over the years that ran 400- 650 thousand kms on original injectors (regular filter changes of course) without components like injectors ever having been serviced. They ran fine and their eventual end had nothing to do with injectors.
Engines are designed to run on our fuel, do the designers and manufacturers recommend it? The dealers certainly do, in a similar way to "paint protection" and and any number of other extras they use to increase their profits.
That's only one opinion though, others will have completely different pov. As I say, it's up to yourself. Different brands of fuel already have additives (supposedly) designed to keep your engine clean. If we look for things that might back that claim we're back to the "Ponds Institute" again. If you believe they help, where's the harm I suppose, helps keep the economy ticking along.
ps. I really think the best thing you can do would be to change your filter regularly, to manufacturers recommendations at the very least.