Plant supports from recycled plastics

It says avoids water wastage. I wonder how it's doing that?? I've looked at the link but my French is rubbish it looks interesting!! This is what I have been trying to do for a few years.

I would love to grow everything but over the years I've begun to realise that as I have to pay for water it's only sensible to grow on any seedling that I think I can use. I have benefited- less cost and time - but my friends, neighbours and any passerby's have lost out as I have half the spare plants available now . I try not to grow things that get "wasted" or use resources and don't get used.I was asked for tomato plants 3 times this week and I have none spare!