For most wrestlers, a big match at a huge pay-per-view is the highlight of their month - or at least, that of their accountants. Being on the major show is generally a great determiner of relative wrestling relevance, and the pay packet doesn't respect the outcome of a worked match; win or lose, the corn comes home just the same.
The other thing a much-sought spot on a Sunday night spectacle offers is security. Anyone bashing heads on pay-per-view can generally be assured that they are in the middle of a faintly meaningful programme pointedly designed to extract money from the TV audience's wallet, and unless it's culminating in a Loser Leaves Town match, can look forward to similarly significant paydays in the weeks and months to come.
Simply put, WWE won't invest time, resources, and Network real-estate in a guy whose future endeavours are on the horizon.
Usually, anyway. Extenuating circumstances mean that in the rarest of cases, WWE superstars have played the Lord Mayor's Show, only to find themselves out on their arse the next day. If only there was some succinct metaphor to describe this.