I dare say some of it can be put down to laziness but, in my case, I do try to find a previous answer before I post a question.
This is not always easy, as some questions are not clear when they are posted, sometimes the site runs horribly slowly and a search for a question can take a long time, and human error also dictates that sometimes you just won't see a previous answer.
It may grouse you that some ask the same questions, but it also riles me when someone replies "This has been answered before" when I have tried to look.