Raider kinda makes me wonder why it's not a Treasure? Except for theme of course.
There's a pretty obvious difference - if it were a treasure, you could play it before you play your other treasures (e.g. copper) and force the discard of a better card. Also, theme is a real thing.
At this point I think that Night cards are mostly a new mechanic in order to not confuse casual players by having cards with Treasure type that don't provide money. All of what we've seen here could easily be implemented using existing mechanics for Treasure cards.
Devil's Workshop obviously doesn't work as a treasure either - it has to be played after your buys. Similarly, Ghost Town doesn't work because you'd be unable to play it the same turn you buy it. I don't see an elegant way to do these concepts without the Night type.
Overall I find the idea of Night cards being for casual players hilarious. The last few Dominion expansions have been manna from heaven for hardcore players, and probably way too much for casual fans. This one looks to be the same.