* The "r" sound is not a native sound in many Desi languages. In languages like Hindi and Urdu, the "r" sound is pronounced as a retroflex, which is a sound produced by curling the tongue back towards the roof of the mouth. This sound is different from the "r" sound in English, which is pronounced with the tongue tip against the alveolar ridge.
* Desis may have difficulty differentiating between the "r" and "l" sounds. The "r" and "l" sounds are both produced in the same area of the mouth, and they can be difficult to distinguish for people who are not native speakers of English.
* Desis may have a speech impediment that affects their pronunciation of the "r" sound. Some speech impediments, such as rhotacism, can make it difficult for people to pronounce the "r" sound correctly.
It is important to note that not all Desis have difficulty pronouncing the "r" sound. There are many Desis who are able to pronounce the "r" sound correctly. However, the factors mentioned above can contribute to the difficulty that some Desis may have with this sound.