A painted portrait is unlike anything else in the world. It’s not just ordering a picture of someone, it is engaging an artist to bring out the character of the subject in a totally unique way. A portrait artist truly creates a "lasting impression" of a subject.
Reasons for commissioning a portrait are legion. In many cases, a portrait is a tribute. Here are some typical ideas:
Remember, a fine portrait lasts for the ages. The archival nature of an oil painting will last almost forever. Many examples of European oil paintings have endured hundreds of years and still look great.