Well, they replace nicotine intake.

You get a measured, stable dose over time. In theory, once you get used to that, you step down the dosage until it's low enough that you can quit without the worst withdrawal experiences.

Now, you have to be ready to quit, you have to be willing to get past the habitual and psychological side of smoking, and you have to accept that there will be some withdrawal symptoms along the way. But they can and do work.

Me? When I quit with patches the first time I quit for an extended time, they worked fine. I was younger, hadn't been smoking super long, and had things to keep me busy in a way I didn't when I quit this most recent time. In between starting to smoke again and quitting this time, I tried patches multiple times without success because of the psychological, social, and habitual influences.

You get out of patches what you bring to the situation.

They can also be very useful for someone that is medically barred from smoking, but not from nicotine itself, or for short term use in most situations.

Side note: I still miss some parts of smoking. But I don't miss addiction, or the physical effects of smoking and the effects of nicotine.

If you aren't ready to quit smoking, patches are damn near as expensive, depending on where you live. Some places they're more expensive than cheap tobacco and rolling your own. So you're throwing money away for next to no real gain. You're better off setting the money aside for when you're ready to quit.