In re: Why talks in Islamabad between the United States & Iran, outcome irrespective, could be arranged, while India & Pakistan continue to refuse to talk to each other beyond what is unavoidable. 

Abrahamic people are more likely to be able to get along with each other. India is a Hindu majority country.

That said, Pakistan has an unhealthy obsession with Kashmir. If Pakistan would be open to an India-China-like relationship, talks could start tomorrow.

There are prominent Pakistanis like former Prime Minister Shahid Khaqan Abbasi who have publicly spoken about the possibility of having a relationship with India similar to the India-China relationship. Former Senator Mustafa Nawaz Khokhar probably has similar views.

However too many crazies have more influence.