Because they have more important things to do...
MENG Online: What others think about you is none of your business, by Peter Engler, 2012-Feb-1
Realize, please, that you can only do so much about marketing yourself and impressing your profile and goals on others. Do your best and then leave it to the gods and move on to another opportunity or activity that offers promise.
Frankly, others probably think you’re terrific. They are just spending most of their time on their own careers and jobs, and all the work it takes to keep them alive and growing.