In the practical life section, there are many activities that involve transferring objects with utensils. These are great tasks to help if your toddler has trouble feeding him/herself.
If you think about it, how often do they get to use the spoon? Average, 3 times a day. For some, that might not be enough to acquire the skill. What they need is more practice.
Do small transferring activities throughout the day so that your toddler gets used to holding and manipulating a spoon. Practice! Practice! Practice!