I agree on the inventory and ammo, but I can see how some people look forward to managing those things manually. There are people that love crafting in MMOs. It's something I've never understood. I think a lot of RPG players are into stats and micro-management. Mass Effect 2 is definitely not a stat or micro-management game. It is designed to keep the story or the action moving. There is a huge contrast to Dragon Age, which I'm also slowly playing. In Dragon Age, every time I find a new item I have to spend ten minutes sorting my inventory, trying to figure out whether it's worth picking up relative to what I'd have to drop and destroy.
I do enjoy loot games, and if they'd gone the route of picking up weapons and armour, I would have been fine with that. In this case you can find tech which you have to bring back to your ship and develop into upgrades by spending resources. I'm wondering if there was a consideration in terms of the game difficulty. With this system they can place exactly when you'll be able to get certain upgrades, and maybe that helps them scale the difficulty. In most RPGs the difficulty can be erratic depending on your equipment. You might get some great armour early and tear through the easy part of the game, but then struggle later if you are not able to get the right set. Or vice versa, you might have poor armour to start, but get amazing armour later making the end of game incredibly easy. With Mass Effect 2s approach, they know you won't be getting upgrade X until you visit a certain place. Maybe that helps. I don't know. It could have been something they weren't thinking about, and they simply wanted to remove micro-management to improve the flow of the game.