Historically at least, one of the significant jobs of a wingman has been to act as bait. With dogfighting, with cannon fire, fighters are most vulnerable when they're trying to shoot down another plane, because they need to be pointing to their target so they tend to be going in a fairly straight and predictable direction. The idea was the wingman would lure one of the enemies onto their back, and then the their partner would dispatch the relatively easy target. This is one of reasons why fighter aces in WWII had such a lopsided kill count compared to everyone else. In order for this all to work, the pilots have to trust each other, and it was certainly the case that some fighter aces put a higher priority on getting kills than preventing the death of their wingman.

I'm not terribly knowledgeable about these things (and most of it is theoretical anyway because most of this tech is untested), but I suspect that there will be a similar mechanic with modern stealth and beyond-visual-range air warfare, whereby firing missles makes you easier to locate and ultimately target, so having a wingman who's willing to act as target practice while another pilot waits for an enemy to betray their location could be useful.