Craft brewers don't do many lagers for two reasons.
The first is that they're "boring". You can already get lots of different mass market lagers, and they're all similar.
The second reason is that they're hard to brew. You can hide the fact that you're a shit brewer behind malt and hops (to an extent). You can't cover up poor technique in a lager. The big megacorps have got their technique down to a tee.