Communicating with suppliers in Alibaba

I am new to sourcing from Alibaba. A lot of people suggest to write very formal letter to suppliers in order to be taken seriously . However I found out that after just writing “Hello” and explaining what i need, they seem to be eager to talk and provide. Am I missing something ? Are these small or low quality suppliers that I am communicating ? Or is it a myth to write a formal letter. Please share your experiences