Raising with rags is a lot more difficult to do in live games than online. for multiple reasons.

Energy. At the end of a SnG or MTT online, you are still relaxed and OK. It doesn't take much energy to sit in a chair pushing a button. The stress is still there a the end, but not as much as a live game. If you play in a live game you are out of your comfort element. The people that you took out are still there rooting for you or against you. You have people noticably watching you to see how you are doing and you feel under the gun to make sure you don't make any mistakes. The energy it takes to play in a live game makes a lot of people give up easier. They feel they have done well already and they will be fine with 2nd place. This theory makes it more difficult to bluff people out of pots. Bluffing is what raising with rags is all about.

Reads. People who get far in these tournaments almost always pick up on reads. I have never had the opportunity to watch myself play, but I would be interested in getting that video. I would analyze what I had and when I had it. It is possible that someone is picking up on this as well.

Chips. In most MTTs and a lot of live games, the blinds are so high at the end that it gets crazy. You may have 500,000 and be the chip leader, but when the blinds are 50,000 / 100,000 you don't have much room to bluff, and people are a lot more desperate to make their move. You have lost your intimidation on them.

Finally, math. In live games you cannot judge pot size, 2X BB, or stack size as easily as you can online. The numbers are in front of you online. The rasing with rags technique is best used when you have a big stack and apply pressure to smaller stacks. In live games, it's not as obvious and sometimes unknown.