Substandard quality of a manuscript is a common reason for a journal to reject it. Some journals, although rarely practiced, require authors to submit editorial certificates to prove that their manuscript has been edited by an expert before submission.
A poorly written manuscript can obscure the main focus of your research. When journals receive a manuscript containing mistakes in grammar and spelling, they assume that the author did precisely edit their manuscript. If the authors are careless with basics of their paper, what about the substantive aspects of their study? When a manuscript is not well organized, it concerns journals that an author is unable to conduct a logical study and create compelling arguments. Our editors cannot conduct your research for you. However, proper English editing can certainly help the journal editors acknowledge the logic and flow of your research!