The lack of airlines' willingness to experiment is bizarre to me, considering they have large fleets of planes and could easily A/B test new technologies with minimal investment and disruption of their regular business.
It's not particularly tempting to A/B test seats which will cost you $500k per aircraft to install. Plus you can't conduct real world tests on equipment which doesn't have the relevant certifications.
They could do focus groups though. Build a few different seating arrangements, pay people to sit in them for a couple hours, and collect their thoughts afterwards.
I'd be very surprised if airlines didn't already do focus group testing of various sorts.
People also don't like to be surprised by their brand, at least in non-trivial ways. I'd predict constant A/B testing of disruptive ideas (such as new seating arrangements or radically boarding schemes) would end up damaging the brand and customer retention.
When an A/B test costs hundreds of thousands of dollars, you might be reticent too.
They used to spend more than that on cherry tomatoes every year. I think a few hundred thousand for trying out different seats would be a drop in the bucket.