"perhaps they won't hold onto the PC for that long and plan to use it as an HTPC, family PC, etc., and will simply move the dedicated card to another gaming build."
"Another reason could be that they want to still be able to use their computer, for non-graphic intensive things such as Internet browsing, email, typing up documents, etc. in case their graphics card dies."
"Not being properly educated on all products prior to purchasing one?"