The challenges of writing concise answers in the UPSC Mains stem from the need to convey ideas effectively within strict word limits. Balancing depth and brevity can be difficult, often resulting in key points being omitted or overly lengthy explanations. Time management during the exam can complicate the ability to refine answers. Candidates must develop the skill to identify core ideas and present them succinctly, ensuring clarity without losing substance, which requires extensive practice and familiarity with the subject matter.