Except to the extent they're artificially depressed by some interference in market pricing (e.g. by politicians or cartels), it can only be because the people are unproductive and/or it's hard to ship stuff to buyers.
I was surprised by this article; I was expecting the answer to be something about lower cost of living or supply and demand. e.g. maybe India has an oversupply of engineers and lower cost of living, which could drive down wages.
"Zoho is an Office Productivity Suite from AdventNet Inc. Founded in 1996, AdventNet is headquartered in Pleasanton, CA with offices in North America, Europe and Asia."