Rogues only sneak attack when they are flanking or their opponent is denied its dex bonus. Hiding must therefore deny dex (as invisibility does) if it allows sneak attacks
Once the rogue has attacked (ie, his FIRST attack) he is no longer hidden. All of his attacks from that point on are NOT sneak attacks as the rogue is NOT hidden.
If only the first attack would normally be considered a sneak, does always sneaky with hide in plain sight allow your to get the others as sneak.
By "always sneak" I assume that your rogue told you (the DM) that he is "always" hidding. *IF* the rogue is hidding (ie, there is a shadow within 10'...which is the pre-req for HiPS), then yes, his FIRST attack would be a sneak attack. Just remember, there are some good and bad things to always being hidden...if the player is abusing this, then it is up to the DM to remind him of the bad things...
Why does a rouge get a sneak attack when he is hidden? Is it because the opponent loses his Dex bonus? If it is because of Dex then is someone with Uncanny Dodge immune to this?
The rogue qualifies for a sneak attack because his opponent can not see his attacker, and therefore is denied his dex bonus. Check the specific definition of Sneak Attack and Denied Dex bonus.
