How to obtain an invitation letter

Hi, Ig i want to go to China as a tourist, ii dont believe there is any reason why the embassy should require an invitation letter from me but this is the case in the lagos embassy, why is that?

how should i be invited to somewhere when i do not know anyone there and i am just going for a short while. Even european countries do not hassle people so much especially with the workers outside the embassy requesting for 250k to get you an invitation letter. this is truly absurd in my opinion and I chose to not believe the embassy is not aware of this.