Anyone know why the tails are usually left on shrimp in pasta dishes?

The tails have a different texture from the fleshy part of the shrimp — a bit of crunch that contrasts with the tenderness of the meat. Although not everyone enjoys this contrast, it can be a desired feature for those who appreciate the variety of textures in their meal.
5. Tradition
In many culinary traditions, shrimp are prepared and served whole. This is particularly true in various Asian and European cuisines where the integrity and completeness of ingredients are valued. Chefs who draw from these traditions may be more inclined to leave the tails on when preparing pasta dishes.
Conclusion: A Matter of Taste and Preference
With a mixture of practical and aesthetic reasons, the shrimp tail saga is one that varies according to the chef’s preference, the type of dish, and the diner’s comfort. While some may argue for the full removal of the tail for convenience, others see it as a flourish that adds to the dining experience. Whether to leave the tail on or to remove it may ultimately come down to personal preference, but knowing the reasons behind the practice can make for a more informed and potentially enjoyable meal.