Why do we have to have company end-of-the-year parties?
「なんで会社で忘年会をしなければいけないの」というのは、このように言えます:
Why do we have to have company end-of-the-year parties?
why = なんで
have to = しなければいけない
end-of-the-year party(またはyear-end party) = 忘年会
また、「いつも」のalwaysも付けて、このような強調の文となります:
Why do we always have to have company end-of-the-year parties?