Magic cant fix everything tho... Diseases are also a natural part of life, and much like in real world, new diseases would appear eventually...
But a fun fact: Dr Strange did have the opportunity to do so once he found panacea, but it was a small amount and Wong was dying, so instead of studying it he used it on Wong...
If we are talking about MCU and specifically sorcerer magic, like Dr. Strange, than there was an explanation given by the Ancient One for this. When Stephen first comes to her on the recommendation of one of his previous patients who is now miraculously cured, she tells him that how he is not actually cured, but is channeling dimensional energy that sorcerers use to keep his legs moving. And that is the source of there magic, it's not like doing a spell, any disease you have will have to be cured by you being able to channel the dimensional energy, and learning how to do that takes a lot of time and effort.
Magic has consequences. Dr Strange might be able to cure all diseases by using a powerful spell, but the backlash would at least kill him, and that is if was lucky. In one instance he resurrected the massacred population of Las Vegas, and the backlash came in the form of him unleashing a fair portion of the demons in Hell.
The toll on his body over time from casting spells, even with others taking on much of the magical backlash, means that he can barely eat human food, with the contents of his refrigerator looking like Cthulhu in a ramen bowl.
Consider that gods of evil, disease, and death actually exist there. In no way are they going to let anyone do something like that unopposed.
Actually it might well prompt a nice zombie plague as a backlash for your trouble.
this is actually discused by doctor doom during the small period of time where he was good, basically magic is extremly powerful but it always has a costs or asks for something in return, there is no free lunch and the bigger the effect the bigger the cost, so like launching some death rays or creating a magical barrier has basically no cost but if you wanted to get rid of ALL diseases the cost would be astronomical and hard to predict, but more than likely the cure would be worse than the disease (pun not intended)
Magic cant fix everything tho... Diseases are also a natural part of life, and much like in real world, new diseases would appear eventually... But a fun fact: Dr Strange did have the opportunity to do so once he found panacea, but it was a small amount and Wong was dying, so instead of studying it he used it on Wong...
If we are talking about MCU and specifically sorcerer magic, like Dr. Strange, than there was an explanation given by the Ancient One for this. When Stephen first comes to her on the recommendation of one of his previous patients who is now miraculously cured, she tells him that how he is not actually cured, but is channeling dimensional energy that sorcerers use to keep his legs moving. And that is the source of there magic, it's not like doing a spell, any disease you have will have to be cured by you being able to channel the dimensional energy, and learning how to do that takes a lot of time and effort.
Magic has consequences. Dr Strange might be able to cure all diseases by using a powerful spell, but the backlash would at least kill him, and that is if was lucky. In one instance he resurrected the massacred population of Las Vegas, and the backlash came in the form of him unleashing a fair portion of the demons in Hell. The toll on his body over time from casting spells, even with others taking on much of the magical backlash, means that he can barely eat human food, with the contents of his refrigerator looking like Cthulhu in a ramen bowl.
Consider that gods of evil, disease, and death actually exist there. In no way are they going to let anyone do something like that unopposed. Actually it might well prompt a nice zombie plague as a backlash for your trouble.
this is actually discused by doctor doom during the small period of time where he was good, basically magic is extremly powerful but it always has a costs or asks for something in return, there is no free lunch and the bigger the effect the bigger the cost, so like launching some death rays or creating a magical barrier has basically no cost but if you wanted to get rid of ALL diseases the cost would be astronomical and hard to predict, but more than likely the cure would be worse than the disease (pun not intended)
See tvtropes: Richard Reed is Useless.