The reason why is unclear, unless it is simply that the Indians are unclean and should not step on pure Islamic soil. From the [1] BBC:

Islamic extremists have threatened Indian cricketers with serious consequences if they go ahead with a tour of Bangladesh this week.

Indian high commissioner Veena Sikri revealed the threat was made in a letter sent to the embassy.

"Bangladesh foreign ministry has been informed about the threat from Harkat-ul-Jihad," Sikri said on Sunday.

Activists for the little-known radical organisation have been arrested in the past for attacking secular authors.