What you do on your own profile is up to you, but I think most of the people here on Steemit is here because they dont need to look at comercials and advertisement all the time. So if you start to make post of different brands or the like, people can get angry and downvote you.
But, Steemit has an own button you can use that is called promoted. Her you, or a company, can pay for their post to be seen.
Hope this was answere to your question.

Kindest regards
@Gyldenhorn
for
@Onebitnews