Most of the weight savings isn't geared for the purpose of customer or the environment, it's for shipping materials from other countries, specifically 3rd world countries....mainly China. I'd rate recyclability as a strong priority of being environmentally friendly as well. Plastic is certainly not one of them. All of those good old machines from the past were made from quality, virgin metal and are very recycle friendly. What happened to all of those millions of plastic outer tubs is DD Whirlpool/Kenmore machines that people threw out? Probably sitting in landfills leaching toxins into our water supply, screwing around with out endocrine functions.
I'd also rate longevity and reparability as environmental pluses. Back in the 90's, it was still easy to obtain most parts and repair most machines back to the 50's, at least from the Big 3 (Whirlpool/Kenmore, Maytag, GE). Today, lots of parts are obsoleted after 10 years from end of production, if not sooner.