As the strength of the race the king's life 'matters above all others'. Because his life is so valuable to the race his life can't be risked. When he faught before he hadn't ascended so although he was technically the king he wasn't actively being king.
He and Beth don't have any children so who would take the 王座, 宝座 if something happened to Wrath. Plus the brothers would be so busy making sure that there king was ok that they could get killed.
As king he has the responsility of the race and also has to deal with the glymera. There is no heir to the 王座, 宝座 and he gave up fighting to be with beth.
Wrath is the last pure bred vampire and 更多 importantly, he is king. Wrath can help the 吸血鬼 thrive and ultimately survive. Would any indispensable leader go 'trolling'?