If your doctors and hospitals were so great they would not be lining up to come here.
It is 'medical tourism industry' less about philanthropic and humanitarian efforts, and even if there is some good deeds and charity involved in it, too much of political point scoring and media hype is not helping it. Indian medical tourism industry needs good vibes, good marketing and all that.
Lots of articles here in DAWN and other media group about these stuff.
As for why Pakistanis are frequenting then, the answer is they are specialty hospitals like Apollo and Fortis/Medanta , runs as business practices, and charges a good amount from overseas, not just Pakistanis. They(Pakistani patients) save the travel and living expenses if they go to UK or for that matter US hospitals, finds it easier and relatively cheaper.
Lots of expats Pakistanis do visit Pakistan for dental operations, many for other medical treatment if they don't have the med. insurance, even that has some ceiling, does that mean US hospital facilities are bad compared to Pakistan. And I do accept these Indian private specialty hospitals are good and with professional doctors.
It is also about demand and supply, Pakistan is a country of 210 million people, lacs of patients going to hospitals daily, long waiting lists and all that.
Another reason Pakistanis in general harbors less animosity towards Indians/India and open to travelling there, than vice versa. Also coupling LOC incidences/terror issue with common folks in Pakistan specially patients are uncalled for and unbecoming, a low brow kind of thing.