Well I sort of see your point OP-ish.
I strongly believe that the current fashion for strapless dresses has gone too far. Wedding dress shop are basically strapless dress shops, with basically the same pattern but different embellishments and skirts. Designers have got lazy and many brides are stuck with strapless whether they like it or not.
I too was glad when Kate Middleton's dress had sleeves as I thought the trend would be bucked.
When i got married 6 years ago, it was wall to wall strapless in the bridal store and I bought the only dress with sleeves in the whole shop. I wasn't in love with it, but I was more comfortable in it than I would have been in strapless.
The other thing is, you now see so many strapless dresses at weddings that they all look the bloody same, it's almost like government issue now!
However, you are wrong to say size 12 up should be banned, as I know several size 16 women who have good arms and shoulders.
My solution is that designers should make more varied designs and wedding shops should supply a wider variety of styles.