It really depends on body shapes, flexibility, where you're sensitive, and stuff like that.

I love frotting, but it does nothing for my wife, and scissoring doesn't work between us. With one of my exes it worked nicely as part of our menu, but only one TBH, and it wasn't the be-all and end-all part of the night.

I can understand why people might think it only works in porn

It can be when done correctly, and when done between people whose body shapes are compatible. But it really depends on the people involved. Good scissoring doesn't look like what they do in porn. You need lubricant, to find the right angle, and it (most frequently) does not lead to orgasm on its own. It's kind of like a much more intimate form of grinding in that regard. Technically it's possibly to orgasm from grinding alone, but just like scissoring and tribbing, that's usually not the goal. It's highly intimate and fun with the right expectations. And it's only fun when both people are into it.