Here is what I think.
First of all, pillowed cubes are not allowed.
However, the V-Cube 7, which is pillowed, is allowed.
Their reasoning is that many of the production 7x7s are pillowed, so they are allowed.
The ShengShou 7x7, (rated by users) is a vastly better cube than the V-Cube.
(
http://www.speedsolving.com/forum/showthread.php?37390-ShengShou-7x7-vs-V-Cube-7 )
(The Shengshou is cubic)
I predict that the Shengshou 7x7 will become (if it is not already) more popular than the V-cube 7.
What I believe will happen is that pillowed 7x7 cubes will still be legal, even when most of the competitors are using ShengShous.
So, lets say stickerless cubes stay illeagal until the point when 2/3rds of the competitors are using the ShengShou 7x7 and 1/3 are using the V-cube 7 which is still legal.
At this point, an illegal cube (V-Cube 7) is now legal due to the fact that there are not many cubic 7x7s, even after they are outnumbered 2 to 1 to cubic cubes.
Many people use Dayan guhongs, zhanchis, lingyuns, and most likely will use the new Dayan 6. All those cubes are available in white, black, and stickerless. That means, the most popular brand has 1/3 of its cubes stickerless.
If this happened, 1/3 of 7x7s are illeagal because they are pillowed, but the rules were changed to let them compete, and 1/3 of all 3x3s are illegal because they are stickerless. Why would we not have stickerless legal?
What if someone just wanted to buy a cube and didn't have enough money and time to buy stickers all the time. They cant compete.
Stickerless cubes are amazing. They last essentially forever and still look new. They are one of the biggest new revelations in the cubing world. Why waste money on stickers when you can have an always new looking cube, all the time?
This argument has been mentioned before, but if stickerless cubes are legalized, they don't really offer an advantage because anyone can go buy a stickerless cube if they think it will really help them.
One would save money anyway in the long run not having to buy all the stickers.
So what if you can see the back color during a U-turn? How many people are really going to rely on that during a fast speed solve where you are turning 7 faces every second?? (If that is your TPS)
In my opinion, having stickerless cubes be illegal is just wrong. I am tired of sticker shards stuck under my finger nails and spending hours of my life restickering cubes. This is crap.
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Edit:
For blindfold solving, it seems just as bad as during normal solving. In BLD when you are looking to examine it, that honestly seems like it would be more useful to try and look at the back colors by looking over the edge than during a speed solve.
It does not make sense that they would be allowed forBLD but not speed solving.
On top of that, more than 50% of people want it legalized. If this was put to an actual vote, stickerless would easily win.