MJ,
Because if someone has enough money and wants to adopt it, they can.
I doubt they will (I think only 2.2 has continued much after the
community abandoned it and then not in a very organised way) but it
leaves the door open.
It should also encourage RMaints to actually post a Request For
Adoption notice / Orphan warning promptly, rather than our July
meeting being told that some developers thought it was abandoned in
April. I think there was no big announcement of that... or I missed
it because of other announcements in April and my shortage of time but
http://koha-community.org/download/ says "the previous releases still
being supported are 3.4 and 3.6." So let's make it less scary for
the RMaint to bow out neatly, right?