That's because of their particular properties.
And again, why do their properties have any bearing on it? "It just is" isn't a viable answer.
Why do they act according to these laws? (and yes, I full well understand that you feel "law" is a misnomer)
Well, maybe because their particular behavior is a direct result of their respective properties?
If they showed a different behavior and other regularities in their interactions they'd have a different set of properties altogether.
Why do they act according to these laws? (and yes, I full well understand that you feel "law" is a misnomer)
As I said above, if they "acted" according to other laws (i.e. showed other regularities in their interactions) they'd have different properties. "Laws" are derived from these properties. Just why is this so hard to understand?
Now why does the universe and all that it contains has these properties and no others? Well, I don't know. Maybe our universe is just one out of many, each with a different set of properties or maybe this set of properties is the only one (or one of a few others) that produces stable universes. On the other hand our universe may also be a science project of a being from an other dimension who made it the way it is because other configurations didn't yield interesting results.
So maybe one of the above scenarios is true or maybe none of them but whatever the reasons for the properties of our universe are, they have no influence on it's behavior.
Whether these properties were intelligently designed or not doesn't matter. As long as they are the same you won't notice any difference and you'll observe the same regularities in each case.