There are two kinds of answer to this question:
- These machines were designed by humans to benefit humans, and they cooperate because this serves humans;
- The machines share memes with each other, so Hamilton's logic of kin selection predicts that they will cooperate;
The idea that artifacts that cooperate to the extent that they share memes has considerable merit. There's certainly a correlation: 100% shared memes often results incomplete cooperation - while 0% shared memes generally results in fairly minimal cooperation which is explicable in terms of reciprocity and byproduct mutualism.
As an example of how the process works, let's look at the cooperation that takes place between a printer and a computer when they print a document together. Without that cooperation, no documents would be produced - and the consumer would be frustrated. This could potentially damage the memes in the devices themselves - for example, maybe the printer will be thrown in the trash if it was identified as the defective component. However, the memes in the printer were terribly unlikely to reproduce directly in the first place. The main way they can influence their own propagation is via copies of themselves in the headquarters of their manufacturer. Part of the consumer's frustration will probably be directed towards the manufacturer. This might affect future purchases by the consumer involved. The consumer might mention the problem to other prospective customers. For example, they might write a negative review or tell the story to others. The cooperation between the computer and the printer happens because of benefit to copies of the memes involved at the headquarters of their manufacturer involved.
This example shouldn't be taken to imply that the effect is confined to computer peripherals, a wide range of cooperating artifacts exhibit cooperation which is based on cultural kin selection.
There are some cases where shared memes in some sub-component or interface seems to be more important than overall shared memes. However, if you view single artifacts as symbiotic conglomerates with components from many sources, this still makes a lot of sense - and a kin-selection based approach is still highly appropriate. There also be cases where shared memes in the associated manufactures (rather than the device itself) seems to be a factor. Consumers certainly use the manufacturer as a clue to compatibility - for example with printer cartridges. However, this is just a proxy for shared memes in the artifacts. If looking to the identity of the manufacturer is helpful, that could be a complication when applying the approach.
Technological kin selection has gradually moved from being a minor factor in explaining cooperation on the planet to being a pretty significant one. As we move towards the memetic takeover, technological kin selection seems likely to continue to increase in significance.