Each individual's 'ideals' differ. Your goal weight is different from the next person and the same applies to fitness and many aspects of health.
Whether you want to compete in races or simply feel better about yourself and build in self-confidence, minor tweaks to a current regime or subtle introductions that have minimal disruption on your current lifestyle can be hugely beneficial.
With a personal trainer, having someone with experience for encouragement and guidance will help you claim ownership of your progress. Research shows that with help, people tend to both progress faster and stick to their goals.