Why is it so difficult to get a job in upwork???

hey guys i was trying to get a job through the site upwork i am a graphic designer and also good in adobe after effects so when ever i see a job related to it and when i am free i submit the proposal there i have experience i have portfolios but i dont know why they dont reply…………………..i am getting anoyed by it.As well as fiverr i tried my service are just waiting at the last but no body sees i have more skills than the people without any skills and selling and getting selected…

Why is it so difficult to get a job in upwork???