you get a better pic top down .......
its pretty much the norm for sellers to do now a days considering you dont need to go through 2' of water to get a pic and the majority of people want a clear picture , corals are top down and fish are in palm of hands.
i find with zoanthids all the color is facing up so from a side ways point of view youll see lots of skirts and not much focus on the actual pattern or color which is usually on the face, having a clear shot from the top down gives a better idea if your buying something true to its name or if its a lemon
now not all corals are like that but for alot top down is a easy way to get the real patterns and colors up front.
you have to remember most sellers have shallow coral beds so going through the side isnt always the best angles.
at the end of the day you could always pm the seller and ask for a side ways shot but lately theres been alot of complaining about having to do more than the average person has time for so i guess it depends on what category your in lol
hope that helps clear it up a bit
cheers
denny