I did wonder that, as an astroturf down the side of teh pitch would prevent the mud tracks they churn up in the grass, but it just looks a bit peculiar to me the way the line runs along the very edge of the grass.
Maybe that's just teh "modern way" and I've not noticed it before.
Indeed it is the modern way. Like you say its stops the touchline turning to mud where the lino ambles up and down. You can see it at a lot of grounds these days.