it didn't make me insecure, it made me angry that I didn't get more money
don't worry about it though. Most people who get money get a smaller amount but its not the end of world.
Getting in can be a crap shoot and scholarships well that is even weirder. Who knows what strategies went into that.
Here are some possibilities i thought of in a few minutes. I'm not saying they are valid, just trying to show how they might consider giving out money:
Attract an amazing candidate who they absolutely want
Attract an average candidate who fits extremely well with the program/community
Attract a candidate who is unique or less represented at that school
Attract a candidate who has a profile or interest that fits well with another school (either peer or higher ranked)
Attract a candidate that the adcom really develops an interest in or feels connection with
My brain stopped working at this point
Don't worry about it though, it would have been nice to have but not having it doesn't mean you are not as good/qualified as those who received them.
At the end of the day, this is the adcoms assessment of the applicants. Adcoms are not the end all be all predictor of success. I would focus on the fact that you were accepted to multiple highly ranked and exclusive programs. That is a great accomplishment in itself, but if it really bothered you, you could always request the adcom reconsider your financial aid offer!