Because title and abstract are very brief and usually added at the very end of the writing process, they often don’t get sufficient attention from the authors. But you can’t underestimate the importance of these parts.
Your readers are very busy professionals who are looking through lists of search results. So the title and – if the title caught the attention of the reader – the abstract are the first things the readers will see.
So you are supposed to ‘lure’ the reader in – without ‘click-baiting’, of course. The readers need to be able to quickly decide whether the content of the paper will be relevant to them, and you don’t want to disappoint them.