alot of spark plug wires can be saved if you just give them a twist before you attempt to pull them off. what happens over time is the heat creates vulcanization. which is the rubber adheres to the spark plug. if you give it a twist first it will break it. trust me wires can get stuck pretty fast. i was working on a 2000 regal gs i had just put wires on it and drove about 5 miles and needed to remove a few wires again and without the pliers that wasn't going to happen.
if you needed to replace every set of wires you pulled off at the job you would be unemployed very fast.
Not exactly. Rubber and silicone don't "vulcanize " to ceramic.
What you are getting is a vacuum seal, The heat expands the air in the spark plug grooves and it will leak past the "Seal' as in that direction it's a poor seal. (Think mason jar lids and their seal..) as it cools the air contracts and pulls the boot tight.
If you pull on the wire or boot, particularly from the rear, it also starts to stretch the boot lengthwise, and the seal and grip get tighter. (Think of the Chinese handcuffs you played with as a kid)
If you grip it near the bottom edge, or in the case of the hook tool GirlnAgarage posted, from the bottom edge, it tends to expand the boot and break the seal.
Dielectric grease helps for making the grip less secure, however it also makes the slight vacuum seal even better; but, I think making the grip less secure overshadows the vacuum. Use the grease.
wned: by GirlnAgarage! 
First time I used it I felt dumb for all the other times I threw fits over plug wires. 
Glad the idea was submitted.
