The situation a person is in, is the best situation God wants you to be in. By going to a rabbi to get a blessing to change your situation, you might be neglecting this fact.
With that being the case, why is it so common to go to big rabbis to get blessings and are there any possible issues with it?
Also, if God has placed you in the best circumstances for your particular mission in life, how can a rabbi's blessing have any effect--no matter how great he is?
This question could be generalized to why do we pray to change our circumstance, but it's already brought down in various Judaic texts, including the Torah, that god desires to hear the prayer of his people, among other reasons such as working on ourselves through prayer and meditation.