I don't think it's 'ridiculous'... would it be better that Oxbridge interviews were delayed until after you knew your score? - No. Would it be better that marking of the papers was rushed so that Oxbridge people could go into their interviews knowing every possible mark and grade to their name? - No.
It's annoying, yes, but that's all. Last year we all did the test on Nov 3rd and had to wait until 31st Jan, this year some people are taking the test even later and still getting the scores in Jan - that's not bad.
Also, even if you did know your score before an interview, I'm struggling to think what relevance it could have. Time may even be wasted discussing the test when it would be better spent discussing you. The LNAT was intended to be an additional part of the selection process, not an integral one.