These are what Ponders called 'elisions' (I admit I didn't know they were called that) and, as is my understanding, are not necessary. They are a linguistic affectation.
Normally you see them in novels where the author uses them in character dialogue to indicate some kind of accent and such like.
I'm willing to have my understanding corrected (by Ponders). If I am corrected I will issue another bonus to monny by way of reparation (to whom I already gave a bonus for the unnecessary usage, but neither did I chide him because it isn't incorrect)
Bore off for ****s sake speccy.
) and, as is my understanding, are not necessary. They are a linguistic affectation.