Opening .pptx files in ONLYOFFICE Documents Editor will not import fonts that are not installed to the system, breaking some slideshows that use custom text (which is extremely common). Since fonts are not easily extracted from .pptx files by the average user, this compatibility feature is important for a productive and pleasant user experience.

Additionally, embedding fonts into MS-Office Suite Compatible file extensions is necessary for complete compatibility for such files (.pptx, .docx, etc).