The reasons people have a painting on their wall:
1. They love it and love to look at it for long periods.
2. They think it looks good in their room, makes the room look better. In extreme cases it may cover up wall imperfections.
3. It is a way to express their own taste. They wish to say something about themselves.
4. They like the subject matter.
5. They know the artist, often a relative.
6. It is a financial investment, they are hoping it will increase in value.
7. Artists may buy work of other artists whose technique they admire or to show solidarity with other artists.8. Collectors may derive a personal satisfaction from discovering an artist and other psychological factors about collecting may come into play.
The reason may be a combination of these.
After getting some input over on my Facebook page I have made some adjustments.
Does this look like a good definitive list?