Because I know many disagree to that. I also know it is not one of the "monotheistic Abrahamic faiths".
And the muslims might have come as invaders, but the islamic faith is still present in india since over 1200 years. You might not like it, but most think that qualifies as being part of that land by now.
Same im europe. Christian faith came mostly by the sword. It is still part of european culture now.