There are a couple of factors that are worth considering. Unlike fiber or coax transport systems, satellites are usually used for very long distance communications. Because of this, it is quite frequent that your link will terminate in another country or even continent. This will make standards compliance and procurement a challenge from day one since you can't guarantee everyone has access to the same equipment.
Secondly encryption standards have to be agreed upon and quite often, equipment from different manufacturers can't be cross-utilized, so you can't just assume that off-the-shelf crypto will be an option to everyone who will participate.. This means everyone has to agree what to use in advance, which could lead to still other challenges. So it's not as easy as the question implies.