38_Cal,
What you say is true, but supposing you are using original equipment that isn't equipped with a bubble level?
But, lets also look at what you're saying. You have shot in the past at Pine Ridge (where've you been anyway?) and you know the wind switches on half a seconds notice as I'm sure it does at most ranges. Plus you can have several flags spaced out down range and none of them pointing in the same direction.
Now you've got this bubble level installed on your front sight. I'm sure you've noticed how they seem to wander off if you don't pay strict attention. You wiggle the rear bag (bad practice anyway but we all do it). Better check that bubble level again. Oops! Missed that perfect condition again!
Now you have to watch that bubble level and the wind at the same time making absolutely sure you catch the same condition for each shot and the bubble is lined up exactly. Considering the level is out on the end of the barrel this can be hard to get set exactly. Not a problem with a "sled".
I will assume you're much better at keeping track of all this than I am so maybe this is easy for you. I look at a "sled" as something that takes this leveling process out of the equation and allows me to concentrate on other things I consider more important.
I assume by platform you mean the front rest?? If so that is leveled up before I even fire a shot. Both fore and aft. It has windage and elevation adjustments to take care of moving from bull to bull. With a properly set up "sled" everything is square to the world for every shot.
If you've used a sled and kept your eyes open as the shot goes off you'll notice the "sled" rise off the table at each shot. With a .38/55 this is quite noticeable. With just a bubble level on your front sight you will have to re-position the level for the next shot. With the "sled" all you do is push the gun back into battery and you're all set for the next shot. Battery of course is the pin the notch in the "sled" goes against so the gun is placed exactly the same fore and aft on your front rest and rear bag and will usually put the sights dead on to the bull. With a scope it can be amazing how close this is. So just a slight twitch of the front adjustments and you're good to go. Saves that few seconds you might need to catch that "perfect" condition again.
The "sled" is not a cure all for good shooting.... as you know. Just a "tool" to help you and to make things easier. Us old guys need all the help we can get.
So I hope you and everyone else I shoot against forgets I said all this.

I'd hate to have it come back and haunt me at some future match like a lot of tips I've given out that are making it hard for me to win anymore!
Hope to see you at Pine Ridge again one of these days.
PETE