The impression I have got from looking quite closely at that market over several years is that the reasons these two aeroplanes were dropped are quite different. Cessna worked hard to eventually create a good aeroplane (flight test accidents showing the effort put in rather thanan eventually poor aeroplane) but just got the cost and marketing completely wrong. Piper didn't put the effort that they should have into achieving a good aeroplane, buying an immature design off the shelf - and got their fingers burned over the sheer number of deficiencies it had - their business case, technically was far better than Cessnas.
If we had Cessna engineering, combined with Piper business strategies, there would be a good aeroplane on the market.
G