Under the Welfare of Farmed Animals (England) 2007 schedule 8
“To enable proper investigation and manipulation activities, all pigs must have permanent access to a sufficient quantity of material such as straw, hay, wood, sawdust, mushroom compost, peat or a mixture of such which does not adversely affect the health of the animals.”
The welfare of pigs code states :
“Environmental enrichment provides pigs with the opportunity to root, investigate, chew and play. Straw is an excellent material for environmental enrichment as it can satisfy many of the pigs’ behavioural and physical needs. It provides a fibrous material which the pig can eat; the pig is able to root in and play with long straw; and, when used as bedding, straw can provide the pig with physical and thermal comfort. Objects such as footballs and chains can satisfy some of the pigs’ behavioural needs, but can quickly lose their novelty factor. The long-term use of such items is not, therefore, recommended unless they are used in conjunction with materials such as those listed above, or are changed on a weekly basis”
Obviously if pigs are being kept outside on earth then they already have environmental enrichment in the land, and will have straw/hay as bedding in their ark, so do not need other materials.
So “pigs must have toys” is not a true statement, either in law or to satisfy their needs for an outdoor system.
Some people do provide toys, and there is no particular reason not to, but like a 5 year old, they do tend to get bored quickly.