That is not the point.
People who buy painting, drawing, photography, etc. art don't do it online. Because online has to many limits ... low dpi, wrong color calibrated displays, etc.
Collectors visit exhibitions, and offline galleries to see the real one. They get the idea how this piece or art look at the wall (at home). Here a picture look great at mobile phone, but as a print 120x120cm at the wall (at home) look like a piece of shit.
And, don't forget an other point: tax, warranty and other laws ...