The simple reason for all of this neglect is that the allotment is 10 miles away from where I live, and I only get out there twice a week. On those occasions, I drown every pot (some of which will have dried out to desert-like conditions) and plant out anything I think might possibly survive. Last Wednesday, for instance, was my yearly Independence Day. It seemed warm enough, I had a few hours and I was sick of watering endless pots in the poly. So, out into the big bad world went all of the french beans, sweetcorn, courgettes, pumpkins and squash. Now, these little plants will probably have had a tough few days since (I haven't been out since, although my father says everything looks alright). They will have had to deal with a sudden flux in temperatures, a lot of rain, then a good bit of sun, menacing slugs, evil cutworms and god knows whatever else. Quite possibly, some will have snuffed it.
That's just the way I roll - through necessity and not a little laziness, this is the way it has to be. And I have to say, most of the time, it works. I have a pretty high success rate with my seedlings, despite the lack of care. I nearly always get a good harvest from everything (some of my challenges are celery and melons, but I keep trying). When I plant out a seedling, I water it in well. If it still looks unhappy on my next visit, I water it again. Then that's it. I haven't got the time to water my whole plot with a watering can (we work off tanks of rainwater at the allotment, so hoses aren't possible). If I started watering crops, they would get used to it; then if I was away for a week the plants would suffer greatly. If I don't water, they put down deeper roots and find their own water. This is a theory of Klaus Leitenberger's - and it works (http://www.giyinternational.org/articles/detail/water_water_water). Even in the drought of last July, I didn't water outside of the poly (except for things in pots). Plants wilted a bit, but perked up again when it finally did rain, and I still got great crops.
The moral of this post? Neglect isn't always neglect - sometimes a hands off approach is the best thing for a plant. They know their own business - to grow, to reproduce - and the least messing with them we do, the better.
To finish, here's some allotments in Lisbon, taken from the metro. They're on waste ground in a ravine - and why not.