Why is the commision so low in adobe stockh

Presumably because they have found that plenty of people are willing to be suppliers at that rate. This is a business and typically companies try to find the lowest buy price at which a suffiencient number of suppliers are still willing to supply. Many suppliers in all trades go out of business because they cannot run at low prices, but so long as enough suppliers remain, the buying business will thrive.

That said, 33% seems to be more than double some other very reputable stock sites. Clearly, if you find a stock site that sells for you, at a higher rate, you might make more money. Adobe do not seek exclusivity.