Politically, Trump had everything to gain and nothing to lose by attending. Despite all his readily apparent faults, it would be fairly easy for the comedian roasting him to go too far, especially in the eyes of his supporters. Despite displaying an obvious thin skin in 2011, he still managed to show up in 2015 (and maybe a few other times). However, as President, he would be expected to do more than attend and self-deprecating comedy is not Trump's forte. If he spoke at the WHCA dinner, he'd show himself to be the least effect president at stand-up comedy since FDR.
Lol.
I mean, oh! How horrible!
But lol.
Oh please that joke's lamer than the man's legs.