Supporting older releases is baggage for any software company. More compiles, more complex testing, more design considerations, dealing with limitations, etc. It hampers them to the point that it makes innovation difficult. At some point they have to stop worrying so much about the user experience on these older platforms, because doing so will impact the user experience on newer ones. At that intersection, you'll likely get a release or two that are somewhat painful to endure. After that, the vendor will simply stop supporting it, looking forward instead of back.
C'Este'La vie... this isn't by design, it's just accepted practice. To keep moving forward, at some point, you have to limit how far you look back.