Anyone who thinks traps are useless really needs to google Tucker's Kobolds. Intelligent monsters fighting intelligently on their home turf would use traps.
I tend to take for granted the rogue can see traps around him in a 10metre radius if he's moving slowly/carefully and the DC to spot is within his search
+ 20 when I DM, therefore if the party lead walks off without the rogue probably hit a trap because there won't be anyone to warn him.
If the rogue is running through the dungeon I'd add a reasonable amount to the DC which would make itt difficult for even the rogue's Search + 20 to spot.
Traps don't just have to be... you touched the door it explodes, make a relfex. A trap can be a puzzle, a puzzle can be trapped, traps can be in rooms with monsters for you to blunder into or wisely lead a monster into setting off.
Look at Skyrim.
Occasionally doors and chests are trapped, they end up setting you on fire or shooting you with darts or impaling you with spikes.
Occasionally floor is covered in oil, just waiting for a firespell or an arrow to the candle hanging above.
Occasionally around the corner there will be soulgem turned into a turret or a pressure pad that will activate a wall of spikes, or swinging pendulum axes.
So what are your options?
Well, in all cases, take a bit of dmg...or die, I've been oneshot by traps before on my assassin character.
Trapped chests or doors, Either disarm them, dodge them once triggered (sidestep that swinging mace and feel awesome).
Oil on the floor, a wise adventurer will lure enemies into the oil and set them on fire. A foolhardy adventurer will accidently set the oil on fire whilst standing in the oil.
Soulgem turret? an archer will shoot the gem out of it's socket, a warrior might raise shield and charge through the pain, a rogue might time dodging rolls through cover to get close and remove the gem manually.
Pressure pad... blunder onto it or lead your enemies to their dooms, or avoid it altogether.
in Skyrim if you get a puzzle wrong, you tend to be rewarded with a hail of poison darts... this is a good and solid indicator that you fluffed it up... better than "Nothing happens"
"But this is a DnD forum, not a Skyrim forum! STFU!"
You can easily transport all of the above into DnD, they all add an extra dimension to challenges, with the ability to increase or decrease the difficulty based on the skill of the adventurer. That's the point of traps.
Don't get me started on the Trapsmith PrC which I love for it's ability to Haste around the battlefield and turn the nearby boulder into a mechanical stone trap with a wise fabricate or stoneshape... let alone the applications if you are fighting a defensive battle with a few days to prepare.
Trapsmiths are Colonel John "Hannibal" Smith.
"Give me a minute, I'm good. Give me an hour, I'm great. Give me six months, I'm unbeatable."