Happens all the time here. It's not always the case that they order them in aspecially. Sometimes the plant supplier will include them in the order. Also, the non aquatic plants seem to sell incredibly well.....supply and demand. A large majority of people that have fish tanks but dont really see it as a hobby, will not be able to keep normal aquatic plants for long therefore its no different to them to have plants dieing in a few weeks.
Do i condone it? No, dont get me wrong.