I am from India, but have lived in US for 7 years. So, trying to answer this based on my experience in both countries.
Because India has a lot of cheaters, especially towards foreigners. One reason for this might be that it is easy to recognize a foreigner in India than it is in US, because of its cosmopolitan nature.
There are cheaters in all countries, but the percentage of such people in India is quite a bit higher than you would find in US. So, even though it may be a little bit more expensive going through an agent, a client would still prefer it to avoid the headache.
PS: I am an Indian, living in India. I wish things were different. Sorry if I offended anybody's sentiments.
I like to blog about various topics ranging from education in IITs to social issues in India and US. All opinions and views presented here are my own and not of my employer.