many small miners are forced to go trading instead of direct mining.
Question is, why would you trade mining shares if you can trade coins? Why not mine where it's profitable the most and trade where it's the safest.
CEX is a good example here, it's not as good in mining profits as other cloud mining sites and not as good in trading as coin exchanges.
CEX is a coin exchange, it has a bunch of trading pairs (30 or so from a quick look plus fiat), their GHS product is just 1 option for a user.
On a related topic about the viability of home mining, this is a good thread
https://bitcointalk.org/index.php?topic=827480.0