They don't swell up with humidity. Yes, I really like plastic. We're still replacing those parts to this day. But the new plastics are stable. Any claim against modern plastic action parts is, in my opinion, simply a misleading marketing strategy.
People buy pianos for many different reasons.
Some are buying furniture. Some are buying into a dream for themselves or their children. Some are buying for status. Some are expert players and are buying for tone quality or evenness of touch. Some are looking for a bargain.