Because most people only buy as many points as they need for whatever item they want to get ripped off for. Why discount bulk points if most people wont buy them unless they need that many, in which case they would pay whatever Cryptic asks, discount or not.
Lemme guess, you bought the Gal-X expecting it to be uber and got bitter when it turns out mounting cannons on a Galaxy-class cruiser was an awful idea?
No, I have not made any C-Store purchases myself... I refer to the c-store as a ripoff due to the insane prices they charge for mostly cosmetic items that should be free as this is not a F2P game.
Add up all the cryptic points that alot of people have used for ships skins, uniforms, new playable races, etc etc and alot of them have spent more money then they did to buy the game to begin with. That is what I consider a ripoff.
Glad at least someone works out that C-Store is cosmetic and does not give any extra gameplay. If people want to spend feel free. Myself I've only brought two thing from C-Store and if really liked look of something would do again. But my money my choice on value or not.
Back on topic, why offer discounts if people would buy anyway. Think Cryptic are just give differant options as save people buying 4 x 100 points.