Post by Clank
It's also because basically it's not true; airline timetables are 'subject
to change' in a way that railway timetables are not, with services
appearing or disappearing at the whim of the airlines (or the whim of
whoever they've flogged their slots to - I'm looking at you, FlyMaybe.)
That isn't a bad idea... on popular routes, sell advance tickets on the
'somewhere between 10am and noon' for September 2014. Exact times will
follow later, and you have the option to refund your ticket if the times are
more than XX minutes from the time you specified. At least you can book the
whole holiday now, rather than playing pot-luck that you'll bag an advance
fare 9 months after booking your air ticket.
Post by Clank
It's easy to sell tickets a year in advance for a service if your
commitment to running it is "we kind of hope so, as long as it's still
convenient for us at the time."
At least in UK/DE/etc there probably will be a train within an hour or two,
it just won't know the exact time so far ahead. It's not as if a
destination will stop being served completely.
On the timetables question, I never understood the June/December dates.
Most countries have some kind of seasonal flows, for example more tourists
using trains in the summer or more business travellers in the winter. The
exact meaning of 'summer' varies between countries (May-Sep for
package-tour-land, August for France, midsummer for Sweden) but it seems
like June-December suits none of them.