People who write well and who speak well are often called upon to do so on behalf of those who appreciate the fact that you can. Like it or not, Jimmy... you're a darned good writer. Your family and friends know it. And thus... you're asked. I've never been asked to do a eulogy, but I can relate to how you feel
When my mom died (I was 28. She was 50), my dad asked me to write a poem for the funeral program (I used to write poetry all the time). I was NOT feeling creative when she died. I couldn't think straight. But I was asked to do it. I know my dad felt like it would be honoring my mother and it would also be representative in a way of the family. What words could I put together that would be just right? How could I express it in a poem that would speak about her... who she was, her life... and what she meant to our family? I was feeling tremendous pressure to rise to the occasion in a short amount of time when I really just wanted to be left alone to wallow in my grief. I managed to get it done. I'm not sure how. Looking back on it now, I'm glad I did it. But it was one of the hardest things I've ever had to do.