Well, I didn't mean that they were the widest technically possible at the time, but what the 'market' can tolerate in terms of manufacture, affordability, even mass appeal for their 'look' is always a while behind the 'bleeding edge' that is technically possible.
Take SLR lenses today. From sigma you can get 8-16mm on crop and 12-24 on FF, but they're not the best IQ at the widest ends, and not very big sellers compared to the widest that the big boys go, 14mm from Canon and Nikon and 15 from Zeiss. And even then, zooms like 16-x and 17-x (on FF) are a lot more popular, from price or portability or whatever reason, a lot of people might just think it's "too wide", but tastes change. And again, it wasn't that long ago that 16, 17, 18mm was 'available', but 24mm was the 'standard'; before that were the days when 28mm was 'standard wide' even if wider was available.
If anything, I reckon the market is pushing the manufacturers to go wider and wider (I know i can't ever seem to get wide enough), soon enough we'll have zoom lenses going to 13mm or wider, and primes maybe to 10 or 11mm. Doesn't mean it'll ever be 'standard' in everyone's kit though...