I think it's natural to assume that there would be a big market for these types of beers, but I think upon closer inspection that may not be the case.
First, consider that most people who now drink craft beer may once have been light beer drinkers who migrated away from that style because they're looking for more flavor and more interesting beer styles.
They're no longer interested in regularly drinking light beer to begin with. Berliner Weiss is usually 3.5ish ABV
Second, consider the economic side.
A craft brewer, if they make an American light lager, will never be able to compete against the likes of AB and MillerCoors on price. There are some very low ABV craft beers, but you don't see them much. I doubt craft aficionados want to pay craft prices for a low ABV beer on the regular.
Their comparable beer is going to be far more expensive, and difficult to convince drinkers they should spend more on that type of beer. Drinkers have been conditioned that they will pay more for say, an IPA, but light lager? We simply expect that to be cheap, when in reality it wouldn't be that much cheaper for a craft brewer to make. Sure, there are less hops/malt, but actual ingredient costs are a very small portion of the total cost of making a beer.
So in the end, even if craft brewers did make more light lager-type beers, I'm not sure there would be a very big market for it. Light beers have lesser sugars to start with, so while you get lesser calories in the end, this also means there's less fermented end products to flavor the beer.
They're essentially mutually exclusive. It's the same as expecting all fine dining restaurants to offer healthy alternatives to their menu. That's not why or how they designed their menu.
There really isn't a strong enough market for small, independent brewers to spend money on testing, manufacturing, and distributing a light beer, which most craft-fans wouldn't be interested in.