Amber, to try to answer your original question, people might change their minds because: they're hypocrites and try to 'do the right thing' but had no intention in the first place; they might be talked into buying the current trendy dog that hasn't made its way to shelters yet (eg Staffies are huge here right now, and will no doubt be filling the shelters later in the year ); or they might not find the right dog on a shelter visit and genuinely change their minds.

[edited to delete stuff about my dogs that Amber doesn't want ]