Shouldn't I? I suspect you're just unthinkingly exporting cultural expectations you've absorbed. I don't believe all cultures treat funerals as necessarily sad occasions, and I really don't like being told what I should feel by someone else (although I realise you probably didn't mean it that way).
(small edit)
In my mind mourning is a very private and too sad an event to have people around, and there is bound to be cultures where mourning is cause to celebrate, have fun, and enjoy life in all of its beauty.
I was born and raised in Poland, a Catholic country, and we do gather after the funeral to mourn and eat together. However, apparently this custom dates back to Slavic times – this may explain the difference between our experiences.
And Ireland is VERY Catholic.