Just crashed into a Lamborghini!

I'm sure you already know it's phonology interfering with orthography - the weak form of 'have' being pronounced schwa+v, which is also the weak form of 'of'.

A mixture of laziness and ignorance perpetuates the error, and you even end up with people using the strong form of 'of' when they're speaking in the present perfect - that shit's fucked up.

I <3 schwa, the most 'successful' of English vowels, and yet virtually unknown - a bit like the phonemic equivalent of Beryl Burton.

ə is what it looks like, for those of you with the appropriate fonts installed.

Be that as it may. I think it's laziness.