It's not because of an allergy. Nor is it because I don't like the taste. In my case, my disdain for these pint-sized crustaceans is totally psychological.
But, there are a lot of people with these strange food quirks. While working in a kitchen on the upper west side, I saw this a lot. Besides from the normal peanut, gluten, dairy and shellfish allergies, there were also garlic, onion, raw carrot, and butter "allergies." In 99% of these cases it was a diner's preference rather than a real allergy. (Often to the dismay of the chef... and the server who pensively relayed the diner's request.)
But, when did the diner get more say than the chef when it came down to the food? After all, aren't we the experts? That's why we toil and train; and spend most our time obsessing about ingredients. But, when did the rules change? When did they get to decide?
I don't eat shrimp. So, as a polite guest, I'll avoid it when it's on the menu. Or, sometimes, I'll eat around them like little land mines. But, I'd never ask the Chef to change his dish. It's a matter of respect! The elements on the plate or bowl all have a purpose. Sometimes it's aesthetic (like edible flowers) and sometimes it adds to the flavor (like tarragon powder). Whatever case, try it once. It may change your perception forever.
That is exactly what happened when I went to Aureole for lunch last week. My former Chef de Partie, whom is now a Sous Chef there, sent us the Ruby Red Shrimp dish. Two peeled, perfectly sous vide shrimp intertwined in a shallow bowl and topped with a crispy rice cracker. Before we delved in, the runner, holding a ceramic sake bottle, poured a clear coconut fumet into each our bowls. The scent of lemongrass and ginger infused the air. The micro-cilantro that was scattered on the bottom of the plate started swimming in the fragrant broth. I was transported immediately to a roadside stand in Thailand. The Chef was right. He knew better. And, I would definitely eat that shrimp again.