That's probably the main reason that i went back to playing FO3. This game generally needs more challenge (it's not a bad game, and exceeds FO3 in many ways). There's not really any places you can walk, that's actually dangerous if you're a high level character. Except for the Deathclaw-spammed locations (which really is more annoying than a challenge).
Also, the thing that the center of the map is the safest location, just doesn't work for me. When you reach Freeside and New Vegas, it's just running between those two and doing random ping-pong quests, like guarding the Silver Rush and collecting caps (nofun for me.)
Let's hope a future DLC will add more random encounters, and more danger. Overall i belive that this game is most focused on the "Good Natured" kind of player (people who focuses most on Speech, Barter, Medicine), while people who puts most weight on the guns/action/challenging kind of gameplay won't get as much out of it.
A fun game, but 1 playthrough is enough for me.
Edit: Isn't there like 1000 threads about this already?