OF course I can't.
MS has locked your online game play in the OS itself, of course you need XBL to play online. Ask yourself this, do you need a service to play online? Have you played online on PC? So many games don't need a central hub like PSN or steam or XBL to play online. F2P games are a good example as well, and they definitely incur more expenses than MS does in providing online gaming to you.
This is the reason why GFWL is free right now. It couldn't monopolize itself like it has on Xbox. With the xbox 360 MS now has a platform where there is no competition in the platform itself, and hence can afford to put a price on online gaming.
If steam was to generate heavy losses, they will most certainly generate even more losses if they were to charge for online gaming. Because steam doesn't do anything when you game online, except for the extra features like achievements.
And why does it matter if something is a handheld, online gaming is still online gaming, it still is the same concept.