"Lack of research effort" (that is, not having made any effort to look up the answer yourself before asking here) is one of the criteria for downvoting a question, and I think people might have assumed (fairly or unfairly) that you hadn't made any such effort.
For one thing, in some parts of the world (such as here in northern England) rowan trees are so common and well-known that to someone from there your question seems rather like asking for an identification of a potato. I laughed when I saw the picture myself, but then I realised I don't know where you live and rowan trees might be unknown there - but other people might not have thought of that.
For another thing, doing a quick reverse image search (that is, a search where you put in an image as input and it searches the Internet for pictures like it) turned up the exact photo you posted with a caption saying what tree it is. Maybe you didn't know about reverse image searches. If not, you do now. They're very useful at times. The sites I use are https://tineye.com/ and, if that doesn't work, https://www.google.co.uk/imghp?hl=en&ogbl and click on the little camera icon.