Why do developers always exaggerate their skills in CV?

“Always” is a dangerous word in CS, do not you think?

For CVs, if I see an impossible/implausible/cooked scenario; Several different types of languages in a short and/or simple career, incompatible areas of expertise, more buzzwords than necessary, any mention of “fullstack development”, and such, that CV flies to the garbage bin, if I have time, in plane form, if not just as a basketball.

Most people forget that CVs read two times at minimum, three if you are lucky. HR (first reader) and upper manager (last reader) does not know anything about the actual content, not just for programming, any engineering position or even sales or accounting. It is possible to fool HR screening with buzzwords and garbage about PL-1 and JS development you did last year. Actual manager OTOH, would just hate you for wasting time, less if s/he can catch your BS in reading, more if it become obvious in the second interview.