I am sure there is no need to swallow. We usually only use blow jobs as a form of foreplay - to get everything erect and ready to go - then go onto other activities before I cum. If you build him up to almost orgasm (but not over the point of no return) then let him settle then do it again a few times before penetration then he will have a more intense orgasm (about the closest a man can get to a multiple orgasm ) due to the build up of more prostate secretions. This technique will have a greater 'reward' for him than watching you swallow (which I never understood the point of anyway...)

If it were the taste then I would suggest he thinks about a change in diet as what you eat affects how you taste but I don't think it is the taste for you but more the texture.