Well some champs are better with ghost(olaf, singed), however having an escape spell is pretty much highly recommended.
Also some champs that can split push well could run teleport (mostly top laners) but you could also run teleport on a mid for some ganks.
But I usually run cleanse on my adc unless im ezreal or graves
Some champs don't need ghost or flash, because they already have their own escape mechanism. While being able to warp twice instantly with a champ skill and flash is nice, it also goes to show you're only effective in extremely rare situations and blasting two spells because of poor positioning. Yeah, it could be what you need to turn the tide, but a tide may not need to be changed if you were using more effective things for your champion.
This is why I believe champs like Nidalee, Kha'Zix, and Ezreal don't need flash.
Speaking of Kha'Zix, I find exhaust/ignite + cleanse to be a good combo on him. He's got a really strong push with his evolved W (which can also slow enemies from a distance) and can travel pretty quick if you level up and evolve his E. So you don't need flash teleport or ghost.
I love it when someone on the enemy team takes clarity. I just let them spam, use clarity, and spam again, then I kill them.
Poll