In addition to what DaddyBuzzwole said, there's a second factor, one which hazard uptime factors into: Life Orb is only worthwhile if it lowers the number of attacks you need to kill the enemy.
When your base damage is 40% to an enemy, Life Orb turns a 3HKO into a 2HKO. When your base damage is 60%, it turns a 2HKO at +1 into an OHKO at +1. You're taking less damage from Life Orb recoil than you would from taking an extra attack, so the item is beneficial. It's also good on a cleaner or revenge killer, where you don't know how much damage you'll need, and so more is better; needlessly taking Life Orb recoil when it wasn't required is far less punishing than leaving the enemy alive.
However, if hazards are everywhere, then any opponent not wearing HDB is going to take hazard damage and get OHKO'd at +1 anyway, or the 2HKO from a 40% hit. In that situation, all you're doing is costing yourself an extra 10% health on each attack, on top of being vulnerable to the opponent's entry hazards. The Life Orb isn't just useless, it's actually a liability.
As offensive power creep increases, there are fewer situations where the enemy would survive in the first place, which also makes Life Orb a useless item - dead from a 105% roll is the same as from a 135% roll, and between increasingly min-maxed stat spreads, wider access to boosting moves, and items like Booster Energy, those scenarios are increasingly common.
Life Orb still has its niche, but mons that appreciate it are less common. It's to the point where the item is starting to benefit from surprise value, scoring unexpected KOs.