Why is the following answer being converted into a comment?
Can anybody express a possible explanation?
Prepositions pose more communication problems for learners of English as well as for native speakers than any other part of speech. In addiction, as "Nortonn S" has demonstrated, there are circumstances when prepostions cause difficulties due to a variety of factors; for instance: "he graduated high school in 2008" or "he graduated from high school in 2008", "he never wrote of it to anyone" or "he wrote nothing about it".
In this light, I hope EL&U continues to assist their members in using prepositions with more precision; especially when ambiguity can arise or when dictionaries are not of great utility to the case.