There is only one benefit I know. It is ridiculously fast, probably the fastest method of bridging. It's definitely not useless, but I think there are three reasons that most people don't use it.
It's really really hard to do. It requires a high cps or really accurate timing and with both, it's easy to miss a block and die.
It's risky. I'm not a high-level player, but I think a lot of high-level players have decided that its speed is not fast enough to justify how easy it can be to fall off vs the speed of ninja bridging.
It takes a while to start it. I've only seen one person do it, so I could be wrong, but it took him a while to get started bridging because he had to aim at the right spot and get his trigger finger ready, which could make you vulnerable to an attack.
Like I said before, I'm not a very good bed wars player, this is just my observation. Imho it's better to practice regular speed bridging (some call it ninja bridging). Even Technoblade who is amazing at bed wars doesn't God bridge (at least to my knowledge) and he seems to be doing fine. =)