I think the reason for that is more to do with history than anything. The original intended purpose of PDFs were to be a print quality final layout. That’s not

I think the reason for that is more to do with history than anything. The original intended purpose of PDFs were to be a print quality final layout. That’s not so much the case these days and Word documents / PowerPoint presentations have supported embedding fonts too so they’ve drifted a little into PDFs territory. But from a generalised and historic standpoint: Word documents were for editing and PDFs were for printing.