I'm very new to learning the guitar, and I'm seeing that there seems to be a lot of talk on the ether waves about learning the entire fretboard and all the chords.

Is this really necessary? Why not learn just the chords that are part of a song and then just make some up ( which are probably already in existence) when improvising?

Should I really memorize and learn to execute all the chords out there and if so, why?