You are correct that gravity, as described by general relativity, is not considered a force in the traditional sense but rather an effect of the curvature of spacetime caused by mass and energy. However, the term "unified field theory" is often used more broadly to refer to a theoretical framework that aims to unify all fundamental interactions, including gravity, within a single theoretical framework.
The pursuit of a unified theory is driven by the desire for a deeper understanding of the fundamental laws that govern our universe. Scientists seek a unified framework that can explain the behavior of all particles and interactions in a consistent and coherent manner. By unifying the fundamental forces, including gravity, within a single theoretical framework, scientists hope to achieve a more complete and elegant description of the universe.
The historical development of physics has shown that unification has been a powerful and fruitful approach. For example, James Clerk Maxwell unified the electric and magnetic forces into the theory of electromagnetism, leading to a deeper understanding of the nature of light and the prediction of electromagnetic waves. The unification of the electromagnetic and weak nuclear forces in the electroweak theory has been experimentally verified and has provided valuable insights into the behavior of particles and the early universe.
While gravity may be conceptually distinct from the other forces, the desire to unify it with the other interactions arises from the belief that a more comprehensive theory should provide a unified description of all aspects of the physical world. It is possible that a deeper understanding of the nature of gravity within a unified framework could shed light on the underlying principles and structures of the universe, potentially leading to new insights and predictions.
It's important to note that the term "unified field theory" can be used in different contexts and can encompass various theoretical approaches. Some of the popular approaches include string theory, loop quantum gravity, and other attempts to reconcile quantum mechanics and general relativity. These approaches aim to provide a consistent mathematical framework that can incorporate gravity and quantum mechanics, allowing for a unified description of all fundamental interactions.
Ultimately, the pursuit of a unified theory is driven by the scientific curiosity to understand the fundamental nature of our universe and to achieve a deeper and more comprehensive understanding of its workings.