What damage do slaters/woodlice do?

[Sillyness]

Hi,
I'm a novice gardener with a container garden so all my veg/herbs/plants are in pots.

I've noticed a heap of slaters under each pot and am wondering if they're doing any harm?

If so, what should I do about them?

In my garden book it says they attack seedling and young plants, they hide during the day. It's recommended to clear them away when you see them and any debris as they breed in these areas and do not venture very far. They carry their eggs with them. Over time that should help. If it's a big problem, get some products from the garden centre. I always thought they were harmless... dd used to call them "her pets" before we got the cats and dog! hmm will take my own advice! I've been blaming slugs and snails for everything.

I just wondered cos where there are more of them, those plants are either yelding less fruit / not continuing to grow (just look the same every day despite big growth in other plants) or plants looking weaker!

Thank you!