We'll said... sometimes, however, take marketing for example...if you don't donate to promote your post (invest in yourself) it won't get out in front of the community...if just posting alone, how will we see it otherwise...with the amount of fellow STEEMians and many bot like posts, in the feed essentially, may get overlooked due to the volume of posts submitted at any given time...hope that helps to see other ways that you can be even MORE visible and be seen / appreciated for your contribution...