mainly because over the years, Amazon has been charging more and more for Prime while offering less and less in terms of Prime benefits; this ad feature is the latest example.
I suppose Netflix is offering ads in their content as well, so I suppose Amazon isn't alone in that regard; still doesn't mean that I don't find it offensive.
To bring this back to the context of sports, I feel sorry for folks that are huge enough sports fans that are locked out of watching content because of streaming rights; I believe Amazon has rights to Thursday Night Football if I'm not mistaken.
"Sean sparks like John Starks, nah, Sean ball like John Wall" - Rest In Power Forever Sean Price.