While we sit on a western toilet, our body typically is in a 90 degree position. The squatting position of the Indian toilet on the other hand gives a 35 degree position to the body. At this position, the body feels natural to pass the stools without having to constrain ourselves.
Western toilet increases constipation. Since Constipation is a bigger factor behind haemorrhoids or piles, western toilets are not recommended in general.