Why would that be a reason not to play online multiplayer? You really have no idea what you're missing. The difference in the amount of challenge that you face playing against a human intelligence as opposed to dumb, unimaginative AI is huge.
This is exactly the attitude that pisses me off--and its displayed by almost every MP supporter here. People who are only, or primarily, interested in SP are either lying or too stupid to know what we lke. (And speaking of which, since subtlty seems to elude you, the reference in my previous ost was to the taunting "come play me online and we'll see who's worhtless." Just the type of crap I wish to avoid. I always play PVE in MMOs for the same reasons.) Ok, here's the short version of why I don't play online, which is largely twofold.
First, online play would largely negate what I find enjoyable about Sins. While I have tried many RTS games (including Starcraft, Warcraft, RoN, RoL, Dawn of War, all the AoE games), it is not a genre that I particularly enjoy. I neither like nor, frankly, am particularly good at the frantic clickfests that make up most RTS games. My favorite genres are traditional RPGs (Wizardry, M&M, BG, Morrowind--but not Oblivion) and TBS (Civ, GalCiv, HoMM, Disciples, AoW, Paradox games--which are much more akin to TBS though billed as real time). I enjoy building and micromanaging my empire and take considerable time considering my next moves. I invariabley play a turtle/development game and combat is my least favorite aspect of these games. Sins is billed as a 4X/RTS hybrid and I enjoy the 4X aspects more than the RTS aspects (though as a SF fan for more than 40 years, I do get a kick watching the battles). I always play the game at the slowest possible speed and probably spend as much, or more, time paused as otherwise while I contemplate my actions. Online play would emphasize the very aspects of Sins that I least enjoy--fast and frantic play emphasizing combat and rushes far more than development.
Second, I do find the game enjoyable against the AI and I have no desire to put up with the macho BS inherent in MP, nor do I wish to min/max every little aspect of the game in order to be competitive. I remember one particulary obnoxious MPer, arguing for more action/RTS oriented play in an MMO forum, proudly recounting how many hundreds (or was it thousands?) clicks per second he could maintain in competitive online RTS play. I am quite willing to understand that this may be fun for you, why can't you understand that it is not fun for me?