I have to say that in these days where food production is no longer bound by the seasons and so few people have an idea of the work that so many put into to farm the land, fish the seas and otherwise produce the foodstuffs that support those who inhabit this globe that this is a good question. Well, I can say that now but when posed it, I had to stop and do a bit of thinking as I tried to contextualise the whole Harvest thing.
For me, the harvest festival is a time to celebrate the food grown on our land and it will always come back to that great hymn 'we plough the fields and scatter' (or for some 'Come ye thankful people come') This then extends back into the whole area of food production and those engaged in it here and abroad, bringing in other food chains and the way we trade both here and overseas (Thinks to self: we do fairtrade for those outside the UK but when it come to trading at home trade doesn't seem to be that fair at all).
The problem is that the things that made us think of the harvest, outside of harvesting that is, were the appearance of Brussel sprouts, broccoli and red cabbage; I can recall potato fields and Swedes all coming in as September got underway and the brief availability of Asparagus told us that harvest time was upon us. But now we get the stuff all year round thanks to the many forms of transport available to us and this has removed the 'seasonal' label that made harvest the feature it was.
But I think it is still relevant because first and foremost we still plough and sow and weed and mow and harvest - the seasons are still there, even though we are no longer subject to them in terms of what is in the shops. The farmers are still up with the lark and working into the dark and harvest reminds us that without the labour of man and the provision of sun, snow, wind and rain (which I'll credit to God) in the shape of the seasons there would be nothing to feed us with and nothing to celebrate. And this is the reason that harvest is perhaps even more important than ever - we need to remind ourselves of just how much we have and to, along with our gratitude for that fact, share it with others.
And so, come the autumn equinox (23rd September) we find churches and some schools still celebrating, sharing and thinking about places and people where food is scarce and they act upon it (often). Gifts of food are given to those who have need and more often these days this is done by supporting a local foodbank. Gifts are given to charities like Christian Aid, Send a Cow and others as part of the recognition that we have plenty and are called to share that.
So, as promised here's my thinking about harvest and why I don't consider it to be a 'no longer necessary' feature of the church but rather something that our society should engage even more fully with.